I don't think the throttle could rotate that far. I think it was mechanically limited to the max allowed boost setting.
Not really... You assign too much MAP and the charge detonates prematurely in the cylinder. You knew your max setting and you set it to that. You didn't ram it to the stops. Sometimes there was a wire, but this was just a reminder (i.e. breaking the wire for WEP, etc). You could abuse the engine very easily in almost any plane in existence. Only takes so much extra pressure to blow seals, fry a cylinder head, shoot oil out, burn the radiators, etc... As powerful as they were, they were very balanced and throwing one part out could/would trash the whole engine. Might get you home in 1 piece but it won't be flying ever again. Even in later years with the F-8 Crusaders I have heard they were jamming the throttles so hard forward on bolters and go-arounds off the carrier deck that they were bending the metal frame plate for the throttle. Some actually cut a chunk out of the metal to allow the lever to go forward more! This was ruining the engines and had several bad side effects, but pilots did it regularly to the point that (if I recall) orders were issued to stop doing it.
So, no they're not just mechanically limited. It's more complicated than that.
