There is more than one document. Gotta read them all. :-)
You will find that we have had to use a number of less than ideal methods to get this working ASAP. There are people who are desperate to upgrade ASAP. The changes you expect to see in the UI will come early next year. For now, we are trying to allow those who are blocked to get by.
I found this in the article that was referred to you, is this what you were looking for?:
What if you have users who have apps or flows, but have left the organisation? How do you upgrade them to proceed with Step 3. of the upgrade?
Seems upgrade fails if not all apps and flows have been upgraded.
Can Admins force or do the upgrades on behalf of the users? Thanks!