You are correct. And bear in mind that for only 1 more Refresh their non-Evocation powers wouldn't come from any Stress Track, they'd just be available all the time.
Also, from a pure game mechanics perspective, powers like Evocation and, say, Inhuman Strength are redundant, since you'll never stack them on top of each other. A Wizard with Evocation and two Refinements invested into it is deadlier on offense than a vampire with Evocation and Inhuman Strength...and probably so is a vampire with Supernatural Strength and Claws (and some slightly different skill choices). Having both gives options, which can be handy, and non-offensive powers like Toughness and Speed retain full usage with Evocation...but it's not as broken a setup as all that.