Capn Bug Smasher; Re the definition of age in the charts in my OP, I don't know for sure, but I agree with your suspicion that it is the age of the aircraft from date of manufacture. It couldn't be anything else really.
The workshop also covered developments in "alleviations" of regulations governing the smaller GA aircraft, which are of interest to anyone who owns and/or maintains such a thing. EG; "Part M Light".
I was stalking a different tiger and didn't take much notice of that, but the presentations (universally of dire quality) are in the public domain and
can all be found here.
Good Luck! They are rivetting reads. One of them is the one with the charts I reproduced.