It's really not. I have no problem remembering or calling up the passwords or emails for my personal, Xbox, current work, previous work, or previous student (!) accounts. And yet Microsoft somehow gets them confused; I haven't ever signed in with this PC or from this ItoP address to my student account, the email no longer works, and it obviously can't access my work document...but something is tied together there and MS insists that must be the account I want to use. Private windows don't always fix it either, there's something shady going on behind the curtain.
Contact support and let them know you have multiple accounts and these issues. I thought they were going to be clueless but they were able to resolve some of these issues quickly behind the scenes.
It does not. I have some combination of my work, school and personal microsoft accounts signed in across a couple different computers. It seems to randomly pick one based on some really poorly inferred context. For example, going to outlook.office.com will (usually) load my personal Outlook email. while going to outlook.office365.com (which redirects to outlook.office.com!!!) always loads my school email.
All of my accounts are meticulously password-managed. The ONLY Google property with this problem is Forms. With Microsoft, the entire authentication system is a disaster. Did you know you can sign into your microsoft account with a security key if the moon is waxing crescent, your computer is at least 3 OS updates behind, and you recite a secret incantation?
I got locked out as an admin of a Microsoft 365 workspace while using password manager. I still haven't recovered the account. You can only recover your account by contacting their support on mobile but they are clueless.
I have a feeling they truncate or santise password somewhere.