Disabling "unicode usernames"

In my Japanese community, I want usernames to only consist of ASCII characters and numbers when users register. Therefore, I have disabled the unicode usernames feature, and the allowed unicode username characters input is also empty.

However, when creating new users, I have noticed that usernames can still include characters other than ASCII characters and numbers.

What could be the reason for this?
Is there a solution available to successfully restrict all characters except ASCII characters and numbers?


This bug also exists in my English community :face_with_spiral_eyes: :

does that user actually get created?

Yes of course. Successfully created with non ASCII characters in the Username.