Despite appearances, centaurs and cyphers were different, though similar enough that the ‘can’t steal each other’s magic’ rule applied to them as well. They had far better control, could use normal magic, had no capacity limits, and could drain whatever and whenever they wanted. Plus, Equilibrium didn’t work on ‘em! But their powers were tied-up very tightly with their physical bodies; they needed to drain like they needed to eat and drink, otherwise they’ll shrivel up and starve to death. Contrast that to cyphers, where despite how limited and uncontrolled their powers were by comparison, it was more or less totally optional to use them.