Yep, your mainline is supposed to get squorshed against a carabiner but the webbing works IF there is enough in the hole for the cam to bite into...I had a similar thought until I remembered the ropeman uses the carabiner to lock onto the rope. It might work temporarily but I’d be worried about the webbing getting caught in the teeth or something.
Kinda like having the the right hitch cord paired-up with the right rope.
This is just a DIY tinkering foot loop that I threw together out of stuff I wasn't using.
A footloop is easy to make, it's not rocket science!