As a spectator and reading the reports -
The primary common denominator in the issue seems to be corrosion.
The crack propagated from the PTFE plug.
AAIB - During one of these tests a crack initiated and propagated from the 4.2 mm diameter hole after it had been deliberately corroded under laboratory conditions prior to the test.
Fatigue life is not a factor so much when you look at the disparity between the fatigue cycles. 167 hours?
MOD 45 and MOD 70 trend happened within ~ 6 hours!
It would seem to me that the corrosion issue needs to be addressed first.
The change in material, higher power, 5 blades and subsequent change in cycle fatigue etc etc are the differences from a Super Puma which doesnt have a problem.
For me there is still a way to go to a conclusion to place the thing back in service.