So, assuming the one guy was correct, water doesn't have a velocity attribute, but he can still move it with wind, or trap someone in ice. Hmm, but given temp was a variable, maybe the state is stuff like moving rather than a state of matter?
Maybe he needs to do something more to raise the attribute than just keep spamming the exact same spell. I doubt this simplicity is everything there is to magic in that world. It's so mechanical, anyway, that maybe he could actually imagine programming code to control a grander spell. Stuff some C into it. In fact he hasn't even tried the curvy trajectory yet.