This might be another bug relating to federation, but might also be relating to caching on their end. Or because every Lemmy application keeps their own archive, it's possible the user display name doesn't federate on a change but only on a post that they can see? (Or not at all, or only on a timed refresh?)
Lets check after 24/48 hours on those links and we'll see what they say after that.
Only for python codebases :(
If only there was a nice php version