I think it's a little ridiculous to limit the player that much, so I'm hoping that maybe it's a misunderstanding. What if I end up finding a member annoying and obnoxious? The update also said that characters would have relationships with each other too - does choosing your three to take with you just override all of that? Perhaps it's story related? In BG2 you were locked into your party once you hit the Underdark... of course once you came back out you could swap people around if you wanted.
