however one must then ask why Cessna then hasn't put out an AD on this specific problem
Very good question, with no good answer, other than the minor quibble that it is the FAA that issues Ads, often on the basis of Cessna SBs, but in this case there was no specific SB. It was certainly brought to the attention of Cessna, and not just from Australia.
My guess would be that the answer was a bit of "too hard basket" and a bit of "SIDS will eventually cover it".
Don't you fellas get it. Cessna do not wont to support these old aircraft
I have heard words to the same meaning from a very senior Piper sales and marketing executive, about fifteen years ago. His view was that small Piper aircraft had a "desired" life of about ten years, then they wanted to sell you a new aeroplane.
Tootle pip!!