Analysed at
that level, the promotional statement is already untrue.
Blocked users and users of blocked IP addresses cannot edit. At a more
extreme level, those with no access to the Internet cannot edit. In my
opinion, preventing anonymous edits makes the project no less open as
long as registration is unrestricted.
This one comes up again and again, and the consensus has always been
"nope, anon edits will continue thanks."