All the footprints MSR sells are identical floors to the tents they are designed for. They have the same coatings and use the same materials. I've been in some wet conditions in the Wind Rivers, Uintahs, Colorado Rockies, etc. and have never had any issues with water getting pulled underneath the tent. This is because of the cut of the footprint (about 6 inches smaller than the actual floor). This is super important if you are considering making your own.

By using a non-waterproof footprint, you allow the water to be drawn through it wetting down the bottom of the tent. I would rather deal with a wet footprint than a wet canopy. Because of the location of the footprint (underneath a non-breathable, poly coated floor and on top of a wet ground) a non-coated polyester footprint will not breath. Instead it will get saturated with moisture and draw that moisture to the bottom of the tent. This is the thing you don't want. It's always best to have a durably coated, totally waterproof, non-breathable footprint.