IIRC QW's client side movement prediction didn't attempt to predict the effects of, for instance, shooting a rocket at your feet/rocket jumping, which meant on high latency connections there'd often be a bit of a delay before your view caught up with where the server thought you actually were. This also applies to rockets fired by other players. Lower latency had the effect of not only making it easier to fire rockets at enemy players, it also made everything seem smoother when people fired rockets at you.
Later versions of QW created from the GPL source release have introduced lag compensation for hitscan weapons, but I'm not aware of any attempts to do so for projectiles.
Projectiles like rockets apply a lot of forces to the player which are not easily predictable. If you fire a rocket and client-side prediction has it leaving your vicinity without collision but the server has someone stepping into the path of the rocket so it explodes close enough that the explosion exerts force that changes your position, you're going to have a really bad misprediction on the player's position, which of course can get waaaay worse if the player launches another rocket while the first rocket's effect on player position has not been sorted out properly.