If the generator has developed a fault, such that it sees "full field" when it reaches cut-in speed, that would tend to apply an immediate full load....the illustration appears to be a straightforward friction-clutch,which, if correctly preloaded, would slip under a snatch-load and save the drive-shaft.
I have no personal experience in this field, but general engineering principles hold good. I don't see how a binding compressor would make a jot of difference to the generator shaft....it is being asked to transmit more torque than it's design-limit will allow....it is the weakest link, whereas the friction washer should serve that function.