That permission is only over editing the title -- it wouldn't affect the display.
It's possible that something might have triggered a user cache rebuild though, as that could trigger a recalculation of this. We have seen add-ons in XF1 that were bugged and broke this. Can you reproduce this for any other users? If so, does rebuilding user caches in the tools section resolve the issue? (Do also confirm that they don't have a custom title set for the user -- that will always override.)