>>717931783
The velocity of the rocket isn't really relevant to an RPG, 99% of the damage comes from the warhead.
Real RPGs and other antitank rockets do have a minimum arming distance of a few meters though.
It's also possible that the full game will offer different RPG warheads or other weapons to bring in it's place. It's a good way to balance the engineer and make it more relevant on infantry only maps.