I thought the Admiral trying to break the crew up the way he did was absolutely stupid and kinda took me out of the episode for a bit, it seemed there just go give Burnham a chance to start acting up again and really bothered me. Remember Scotty in friggin Relics? That was only a few decades out of time and he was completely lost when it came to the tech. Even Picard didn't like using holotech on the ship in Picard. How the hell are they gonna be reassigned effectively?
When Vance said 'reassigned', I took it to mean that he would have the discovery crew maintaining the 32nd century roomba's that vacuum Federation HQ or locked in a padded holodeck somewhere. Either way I doubt Vance would be assigning a bunch of ancient starfleet officers to the Voyager-J or the Constitution.
Edited to add: I think Vance was testing Saru and Burnham to see how they reacted. He's still not convinced at this point that that the crew of Discovery aren't from some hostile temporal war faction