This is something that fascinates me. In the British Empire, people from regional UK backgrounds which had deep problems with the centralised Southeast England establishment (and still do to this day) often rose to fairly high positions. For instance, the military officer whose campaigns won the British East India Company control over Bengal was Hector Munro, born and raised in a village in the Scottish Highland district of Ross. The reason was, of course, that Munro was Scottish and only the most bigoted of Anglocentrists did not see the Scots as part of the "in-group". As a result, a Scot was allowed to rise to the top of the UK's Indian military hierarchy with practically no objections. The Viceroy of India who began development of the Indian rail network was another Scot, George Dalhousie. The same took place on numerous occasions, with hundreds of people from outside the London commuter belt rising to the top of the UK's power structure. They were different from the elites, the primary beneficiaries of the Empire, residing in London and SE England, but they were still part of the in-group. Many of them were still zealous British nationalists and imperialists. If the Galactic Empire has a policy of Humanocentrism, why isn't there a broad variety of humans in leadership positions? Non-white humans, human women - they're all part of the "in-group", are they not? However, the only powerful Imperial non-white human I can recall off the top of my head is Oron Jaeger of the Fel Empire. Clone commanders seem to make up most of the non-white Imperial military elites in the EU I've read. It's intriguing. Of course, I've seen the argument before that the Empire idealises white humans over non-white humans and that the Core-centricism influences where their officers come from. From what I know of Earth's history, that argument doesn't sound very plausible as an explanation for the complete lack of non-white humans.