It's not an oversight. it works this way by design.
Because it's a GAME, so if you don't make the player at least tangentially aware that they are missing out on something, you'll have hordes of people stuck and raging sometime later "HOW WAS I SUPPOSED TO KNOW THAT I MISSED SOMETHING IN THAT AREA?"
Anyway, yes, it's a mod and one of the fastest ones that we got after the release.
Whats the point of traps when you notice them by 4 failed perception checks when you approached that floor feature?
