Our munitions are zero diameter vectors. If they miss a vehicle model's LOD3 surface by as little as a micron, it's still a miss even if the fuze of the round itself might already have the diameter of a thumb, and the round itself a full 80mm.
That no fragments hit the BMP may appear not so likely, but again, if the round has a sufficiently high velocity the counteracting fragments might still be carried forward a little. Also, in our model the number of fragments that go to the rear is small as the M830A1, being a HEAT round, must have a base detonator that lets the HE filler burn from the rear towards the front, so only the part of the round that provides the rearward containment of the detonation can generate fragments (which would largely be the tail boom and fins). In our model, if the round's impact velocity is bigger than ~875m/s, no rear-facing fragments are to be expected.