I think those cases broadly line up with tdr's statement: they were contained engine failures that didn't impact the aircraft beyond the unexpected loss of power.
Not like a turbine or fan disc failing and tearing through the airframe.
That's not to say that engine failure can't impact safe flight, especially on a helicopter, but it's still much less likely than a disk failure.
To throw a very rough guess out there, are we at about 200k hours per IFSD but maybe 20 million hours per uncontained rotor failure? Couldn't find figures for the latter newer than 1980s on a casual search.