wouldn't it be all that much fair to say that "kamuiland" is technically kaguya's dimension anyway? she gave birth to chakra and the sage, who gave birth to doujutsu and ninjutsu, correct? by logic, she wouldn't ever have to be there to be "synced" with it. more over, one of her main abilities is to pass through multiple dimensions. for BZ to state the 5 we know of doesn't mean that those are the only places she can go to. for all we know, those five might just be the places that she resides in or reigns over. she was sealed off from earth, but never once have i read or saw anything related to her being dead, because she never was. she was "sealed off" and imo, sealing off its removing someone and barring access to whatever dimension they previously were in. RDS sealed off oro's arms and kurama, both came back. sasuke was pulled into oro's dimension, but he manipulated it and came back. the gold and silver brothers were sealed in the goard, but never once were they stated to be dead, or rather dead again lol. basically, kaguya has access to all thats tangible. obito can be intangible on earth, but clearly tangible in his dimension (as seen when kakashi busted his guts) and if kamuiland is tangible, i have no reason to believe kaguya cant go there on her own or get out on her own.