Thing is - facing direction isn't a thing in the tabletop system. It makes sense if your CRPG has a literal backstab system but that's not a thing in D&D5 because it's fiddly and bound to cause arguments over silly things like the orientation of a miniature. If a monster's FOV was a straight up radial flood and they would look around or go, "I 'eard something!" every now and then it would be more of a challenge.
