u/CleoMenemezis explained a little better on the Reddit thread about it, but a tl;dr is:
The corners are currently drawn on CPU and it is slow, and the way it’s implemented is hacky, which could cause artifacts and made impossible to be used with themes.
Awesome, thanks. Definitely looks somewhat more generic now, but it’s not as bad as I thought either, i.e. it definitely still has a recognizable aesthetic.