I have only noticed this behaviour after our organisation enforced restrictions on what users could do on personal devices (e.g. preventing download of data), though I can't say that there's a direct link. As part of this, though, we were advised to enable Microsoft Single Sign On suggests, which I did (this might be why authenticating to something else worked for me).
The main reason I use Firefox, though, is because it allows me to create multiple separate profiles, where I am authenticated different users (not the one with which I log into my laptop). Many of us have admin accounts, test accounts, etc., which we use as part of our daily work, and I find switching users in Edge to be klunky at best.
I hope we are not going back to the bad old days of having to log in to our devices as admin in order to work.