The "skinnier" slide models, like the 5.7, and micro compacts (Shields, Bodyguards) are cut for the modified RMSc.

The wider slide models (full and compact) have a large, rather generic cut to accommodate a variety of footprints. Plates are needed to provide the correct recoil post locations, and fill in any gap for shorter red dots.

Here's a link to a page with various red dot footprints.

Footprints/Mounting Standards on Red Dot Sights - Optics Trade Blog