I think it has to do with the diameter of the outlet. Smaller outlet = higher speed but CFM is what matters for a blower. Cubic feet per minute. That’s how much volume of air it can move.
I don’t think it was intentionally designed to pump water, but I’ve seen people use them as a pump through the side vent. Works, but I’d say it would void the warranty haha it’s not exactly a water tight seal inside that separates the impeller and the motor.