> ...Maybe someone from HR worried about secrets being shared in a chat?
Your phrase there immediately made me think of that Catbert evil HR director character from Dilbert...which is exactly the kind of thing he would want to have setup! :-)
This is very true, and hugely problematic. As a consultant I have to use Teams with 3 separate clients right now, which means signing in to 3 different Teams tenants - Microsoft SSO does not like that at all.
I have a personal hatred for MS because of their long history of building shit like this, but I hoped that working for a different cloud provider would keep me away from that ecosystem - it was legitimately a positive benefit I perceived about this job when thinking about the move. Alas, the cancer of MS software gets everywhere by virtue of being effectively free for anyone using Office.