Of course! My memory is weak, though, and your username here doesn’t match your email address in my notes. 
Yes, I’m pretty sure that Memberful is what’s doing that. I know that Patreon has stupid usernames as some sort of “security”. I’m not sure whether Memberful requires stupid usernames or whether people have the chance to change it but just don’t bother.
The best way to find out would be to start anew with a new memberful account and see what the process looks like to a new user. Responsible community organizers do that as often as once a month, I think. I’m not that responsible.