Q: Action Required: Your AOL Username login must transition to Apple ID

Same here;  I logged out, logged in, was not prompted to change anything. In fact when I went into the Security settings to amend the user name, it wouldn't let me!

That legit Apple document is the most confusing thing I've ever read!  It doesn't state at all clearly whether you should or shouldn't and even contradicts itself and leaves half sentences unfinished. Surprised there aren't more queries in this string!  I will be damned angry if it all goes "apple-shaped" on 31 March!