system
A chat on subreddit /r/pcmasterrace
human
Everyone is commenting on the divot. I think OP means the literal hump in the pcb where the connectors are.

I’ve never noticed it before. Been building PCs for nearly three decades

Did some digging and yep, it’s normal.  TIL
gpt
I'm in the same boat. I've built PCs for years as well and havn't realized. :D The more you know