CT Moff Jerjerod’s appearance in The Empire Strikes Back.

And why is that needed?

You wrote earlier;

We see the shuttle in RotJ, first with Vader arriving on the DS2, then the Emperor arrives, the rebels use it and Vader uses it to go down to Endor and back up again. Vader used the shuttle to go from an ISD to the DS2, most likely the emperor did that as well. He did not go all the way in that shuttle.
So it is a shuttle and Vader and most likely the emperor uses it to go from a capital ship to the DS2 or from the DS2 down to Endor. So it is a means to get places where a capital ship can not land. So nothing much special.
Why is there a need to introduce it in the previous film?

ESB did have a shuttle scene earlier, when Needa went from his ship to the SSD. It is a very short bit but it is not the same type of shuttle used in RotJ or by Vader in the ESB SE.
So if there is a need to show this shuttle, have it when Needa goes from his ship to the SSD.

I have not come across anyone that were confused about the shuttle in RotJ or found anything odd about it.
And if Lucas added it to ESB just so that people would not wonder, then that also sounds like underestimating the intelligence of the audience.

New ships were added in RotJ, the big Rebel ship had not been seen earlier and that was fine. Some new types of fighters were added as well. So why "explain" this?

Bye for now.
Old Stoneface

 

It’s not for you and me. I’m just saying what I believe it’s reason to be inserted is.

Seeing Return of the Jedi for the first time in ‘83 I thought it was effective when the shuttle majestically drops out of the Star Destroyer for it to be a new ship and on that first viewing you don’t know who is on board until the flight controllers on the Death Star announce it.

The way the wings of the model unfold is movement like we haven’t seen before from a starship in the series.

All of that sequence is very nicely handled. The CGI counterpart in ESB by comparison isn’t nearly as fluid or pretty to watch.

And that gulp Moff Jerjerrod makes just before Vader debarks is an excellent moment. It’s a funny and humanizing detail. That’s how any of us would feel if Darth Vader paid us a visit at work. (The plotting Moff who tries to go toe to toe with Vader in early drafts really doesn’t make it into the movie Return of the Jedi. He wouldn’t gulp from anxiety,)

But the fact remains I believe an effort was made to show the folding wing shuttles and normalize them before RotJ. You mention the new ships of the rebel fleet. The fleet is revealed incrementally. Empire gives us then Medical Frigate and the Rebel Transports which the other new ships in the Rebel fleet design wise extend from. But even here we see an Rebel
Style transport incerted into A New Hope normalizing that deign too. (Also not necessary)

Your other exsamples are also incrementally introduced over the series.

Perhaps Captain Needa’s shuttle being an anonymous design shown for only long enough to visual convey travel
between Star Destroyers was another reason Lucas felt compelled to show the later shuttle more. (Needa’s Shute is a TIE Bomber with inverted wings right?)

At the end of all this the reason could be as simple as Lucas really liked the design of the Imperial Shuttle and those wings he wished I they’d come up with it earlier for the series. The special editions allowed him to edit those in.

I’m not trying to justify that reason just saying I think it is the reason.

 

It made more sense to replace Captain Needa traveling to the Executor in a Lambda Shuttle and not the TIE Bomber/Boarding craft than insert Vader boarding the shuttle and then landing in the SSD docking bay. But I guess GL thought the audience wondered how Vader gets to the Executor when we last see him telling Commander Desanne to "bring my shuttle", even that wasn't in the earlier drafts of TESB. The whole telepathic exchange between Luke and Vader wasn't in the earlier drafts either, so it's possible that GL was never happy with the ending but at the time didn't want to step on Kirschner's toes.

 

Captain Needa's TIE shuttle is really tiny unless you're watching the film on a big screen, so I honestly wonder if changing it was considered at all.

In fact, in the SE Lucas couldn't even be bothered to replace the windows behind the stormtroopers who surround Han and Leia by entering from the hallway outside the Cloud City dining room, even though when our heroes walked through that hallway just moments ago those windows were replaced with transparent CGI glass featuring brand-new panoramic views. (It's never been fixed.) So I have to suspect many of the changes might have been Lucas' spur-of-the-moment whims rather than long-desired alterations.

 

Visually it would have been too cluttered to CGI the windows for that iconic shot with the stormtrooper - glad it was left untouched. So they split the difference. If it had to be one or the other I’d go with no CGI but I do like how it opens it up.

Kirschner came back to work on the Special Edition of Empire with Lucas. I heard an interview where Kirshner talked about some changes he wanted made and what he added - I forget which ones. I’m not saying he had final say but Kirsh was at least consulted for input on the changes Lucas wanted making it a collaboration. He was still the director and Lucas his boss as executive producer.

Jedi’s director passed away so wasn’t available making that and A New Hope SE overseen by Lucas alone.

 

ESB is that good that it didn't really need much adding. Who knows maybe Lucas just added the shuttle & Jerjerod scene because he could and felt like he had to add more just for the sake of it to justify its 'special edition' status?

 

Or justify the audience paying again to see basically the same film, both at the cinema and with home media releases.

 

I always found the falling action in TESB was at its weakest at the getaway from Bespin, especially when they are in the air again. The pace slows up considerably, and adding the notion of Jerjerrod, nuances of shuttle craft and so on doesn't, in my view, do service to the structure of the plot. These are all splendid details which are retrospectively banked upon in ROTJ and thereafter. But continuity for its own sake would surely end up damaging all the constituent parts and stories. That comprises one of the complaints (albeit disputed) of the special editions.