Pop rivets loosen, loosen in a way that cannot be tightened. They should use engineered bolts/nuts secured with locktite. If those do slip, they can re-tightened. Pop rivets must be cut off and replaced. You won't see pop rivets on any other cars, not since the 1940s. ("Blind" rivet are different than pop rivets)

If they are pop-riveting, then I assume they are doing this on the cheap and are also not treating/protecting the metal. They are probably just drilling through without worry about future corrosion issues.

Bolt + locktite. Then refinished/repaint/treat the underlying metal to prevent future corrosion from new hole. The pedal is now in metal-to-metal contact with the pan, in a damp environment. That means differential metal issues.