The world loading screen usually doesn't fully form when 100%

(The affect version thing I haven't tested all versions) 

This bug happens randomly, so all you need to do is load a world and there's a chance that the forming squares in the middle don't fully form at 100%

(Note: This happens in 1.14 Pre Release 1 too, but for some reason I can't put it in the version area, alongside many other versions)