When I think of fragmenting rifle bullets I think of exploding varmints. Wouldn't a bullet like that just blow a hole in a deer without penetrating?
I would think that was a possibility, if it hit bone like a shoulder or rib. It might be possible, maybe even probable, to blow apart into fragments that never make it to vital organs and thus fail to incapacitate the animal. The animal might die later of gangrene.
A few years ago our younger son killed a buck that was on its way to dying on its own from a previous superficial wound. He said it was moving slower than normal and acting different than deer act. Upon examination it looked to us like a combination of poor shot placement and poor bullet selection that caused damage to soft tissue but not to any organs. Apparently infection had set in and that led to blood poisoning and gangrene.
When we cut into it to field dress the animal, the meat was basically rotten and unusable. The game warden said the old wound was probably no more than a week or so old.