Another interesting point is that usually crafted sets are made universal, meaning both magicka and stamina cause them but not this time.
The 4p bonus on this set grants both weapon damage and spell damage. So I'm assuming that you are referring to the max stam and stam recovery on the 2p/3p bonuses. In this case, I think that's because those two bonuses are there to support the stam cost of breaking free. Same reason why so many magicka players run shackle, so that that they have the stam pool and sustain for things like CC breaks.