Your original comment stated that covert stutterers do silent blocks while overt stutterers have repetition. I was just saying that's super not the case. Overt vs covert doesn't change the characterization of one's stutter at all. A blocker while covert will likely still be a blocker while overt. They will experience less severity, that's it. You seem to be under the impression that silent blocks are just a secondary avoidance behavior (I think)? But that's not the case, either, and may be at the root of your misunderstanding. People don't choose to (or condition themselves to) block any more than others choose to (or condition themselves to) experience repetition or elongation stuttering. It's just another way of stuttering, that's all.