I have personally witnessed this.....Over the 1966 Thanksgiving weekend in Wilderness State Park, tip of the mitt in lower peninsula Michigan, ...I was about 13, dad was in front of me when he holds his hand up and turns and holds his finger to his lips in the international sign for "ssshhhhh"
I didn't see anything until he pointed under a short thicket of cedars...a doe was bellycrawling under a blow-down through the mud and slush. She didn't have anywhere else to go that didn't expose her to us visually.
Only time I ever saw it....but it make me believe that deer do this when they think they have to..we just don't witness it.