Polyfuses 'blow' in a fairly traditional manner and the fault current falls back to a very low level - basically enough to confirm the fault remains.. After all fault current ceases they fully recover over a number of hours to being fully conductive again. So no they do not sit at 125c in an overload state as a protective resistor might.
The issues are :
* they do not cut off all current entirely
* Their correct operation under all cyclic short and recovery conditions is not generally specified (i.e they are seen as an occasional safety precaution not 100 cycles a day etc.) although it might have been tested in this scenario
But unlike traditional fused they are less sensitive to impact forces while in operation (pretty important in an ELT) and they can recover to allow normal operation after a temporary short circuit is removed. For an ELT the latter two factors might be considered valuable