It implies that arrows performed alot better aerodynamically. In the future with WSE I'd give bows a lower friction value than crossbows. I agree though that the 1 slot crossbows have a too high starting speed. The ones with the steel bow(2 slot) are fine in my opinion.
I don't disagree that aerodynamics could be a significant reason, but as mentioned, in the Warband universe all missiles have the same physics. The way the Warband engine handles this is by giving crossbows higher damage (representing a potentially higher muzzle speed and more devastating missile) and low missile speed (representing worse aerodynamics, causing them to drop faster). Bows on the other hand get reduced damage and a high missile speed, giving them a longer trajectory but causing less damage once they hit.
Now, for some reason, bows in cRPG have less damage
and a shorter trajectory. It doesn't make sense from a game balance point of view, nor from a realism point of view (which I think we should just ignore, but still).
If you were worried about Strategus, I would have done this:
http://forum.c-rpg.net/index.php/topic,10317.0.html