Rabbits killed by a fox holding a looting 3 sword do not drop rabbit's foot

I created a rabbit farm, put a fox in the killing chamber and gave the fox a looting 3 sword. However when it kills rabbits using the sword, the rabbits do not drop rabbits feet.
Not sure if this is a bug or intentional, but if looting 3 is used, surely they are supposed to drop feet?
I also tried this in 1.17.1 and 1.16.4, still no feet drops
I tested this for a long period of time, hundreds of rabbits killed and not one foot drop.

The looting however, does affect the hide and raw rabbit.