Slots in the rear parcel shelf, what are they really for? Seatbelts?

Cudas don't have pkg shelves,lol.
They shouldn't even have rear seats cuz the fold downers weigh 70 pounds!!
Thank goodness that weight is almost right above the rear tires, where the 35 pounds worth of Dynomax mufflers are hanging!
I know I know, you don't see the relevance. Me either I'm just banging up my post-count.
I think my smogger Darts had those back in 73/75