That's been the case for a while, i'm sure it has come up before and there's some tech debt or external system (maybe the android and chrome account switcher in

That's been the case for a while, i'm sure it has come up before and there's some tech debt or external system (maybe the android and chrome account switcher integrations?) that prohibit them from changing it without a massive user-facing behavior change. For bard specifically, you can do ?authuser=x where x is the account number as defined by other apps like Gmail or Drive.