"What user have been telling us is that they want 3 or 4 microsoft/office 365 accounts and for none of them to coexist in a single browser. Users have also told us they want each of their office 365 accounts to be crippled to a different degree depending on which organization is inflicting office on them, so some accounts are browser only, some accounts can use desktop, some accounts could use desktop but can't."
Microsoft 365 UX team, probably.