best response confirmed by deejinoz (Contributor)
Yep. To fix the product name weirdness and the other authentication cr@p hole it had sent me down, I did the following:
1. Used SARA to do a scrub removal of Office, which appears to have also removed Visio (weird as, strictly speaking, Visio is not a part of Orifice).
2. Clean installed Visio Pro 2019.
3. Clean installed Office 365.
4. Risked it and sacrificed a ferret, while wearing sheepskin chaps and standing on one leg. Only a couple of days out from our southern hemisphere summer solstice, which was only on Tuesday.
Result: The Microsoft demons were satisfied with my offerings and Visio now just says it's Visio Pro 2019 and not part of Office Pro Plus and Office 365 still says it's for enterprise apps and not Pro Plus. All the sh!tty authentication errors in Outlook are gone and auto-mapped mailboxes don't just bugger off, in my second Office 365 login.