I’m guessing it’s written for bipeds and not quadrupeds. It’s measuring from the center of the collision capsule. In your case it’s basically the animals center of mass (in it’s middle).
The ledge detection will start to work once the middle of the animal starts crossing the set boundary point.
You would have to write some custom logic doing for instance a sphere trace in front of the animal probably around where the feet are to check if you have an floor in front of it, same for the back if the animal can walk backwards.