[Overdriven]

If the throwout bearing failed that would mean it would no longer spin on the clutch finger side. So when the clutch side contacted the fingers on the pressure plate there would be metal on metal grinding. A more likely throwout bearing issue that could explain your issue is the throwout bearing not sliding easily. I forget what the surface the throwout bearing rides on is called but that could be gummed up, rusty and no longer smooth for the throwout bearing to slide on. Since you say engagement is fine I'd say this is the most likely issue.

But I wouldn't totally rule out a problem with the pressure plate either.