I hear you Iron, these parts most definitely don't just come off the shelf...
I guess that this is where HUMS can really show its benefit via type-proving each critical component, in this case the shaft in question. With two key indicators, namely MOD-45 and MOD-70, the manufacturer is obviously confident in early diagnosis via monitoring.
I'm curious now as to how many AS332 types have similar bevel gear shafts and why they were not included in the EASA AD. I can only assume that the shafts with proven TIS records are by default deemed airworthy. However, how many shafts have been changed out over the years and are any of the suspect ones still in use?
For me over here we only use S92s these days, so we have our own problems!
Safe flying
Max