Just to add to this story.
A while ago I also reported this particular graphic glitch on the official Apple Support forums.
10 minutes ago, someone from Apple called me to ask me if I installed the 10.12.3 update and if I had the issue since.
I told them I installed it when it was released and that it didn't happen since.
The fact that they made this call to check indicate that they probably expect this patch to solve the issue even if it wasn't in the patch notes.
Good news.
A while ago I also reported this particular graphic glitch on the official Apple Support forums.
10 minutes ago, someone from Apple called me to ask me if I installed the 10.12.3 update and if I had the issue since.
I told them I installed it when it was released and that it didn't happen since.
The fact that they made this call to check indicate that they probably expect this patch to solve the issue even if it wasn't in the patch notes.
Good news.