It's impossible to know until you do the actual questline htere, which will likely explain everything you want to know. I doubt it's only for nostalgy purpose. The planet could old ancient artifact, it could be a hidden facility, maybe it old rare minerals. There are countless possibilities. But it's very unlikely to be nortalgia only.

The QUEST is still in game, but I was refering to everything else that was changed. Back then, it's likely they hadn't set on Satele look. So, considering her young self is based on a real person, it make sense to see her young in game. It's likely later they realized the time gap between the game and the trailers.

The E3 trailer is irrevelent, it was a while ago. Things changes between stuff shown in gameplay trailers and the actual game. As a game tester, I can assure you of that, I've seen it happen to nearly all games. I personally haven't seen Satele Shan in game yet, but it's normal that she would appear older. As for the hologram thing, it could be a mistake from the dev, I'd say report it, the game is not fully stable yet, I've seen many bugs in cutscenes, like cloth and hair color being wrong, eyes disapearing and such. Or it's intentional, to decieve you into believing your character is talking to a young person, in case you're a sith spy.