[2020] Comparison between what the attacker actually sees (above) and what the killcam shows (below). The killcam makes it seem that the attacker missed all shots and got a kill behind cover.

I don't know if this is for every game, but for SWS (and probably a bunch of others), the kill cam is the engine recreating an approximation of what happened, not a 1:1 recording. So yeah, there's going to be some weirdness every now and then, especially in a fast-moving game with bright lasers for the primary weapon making it more noticeable than a tiny bullet.