The answer to that would be that transmissions never reach temps where a high-quality dino oil would break down or lose viscosity, in fact our motors don't either. At least not w/o siezing, synthetic or not.
The bottom line is that it is your car, use whatever you want. It is just a matter of whose advice you value, "Sweet Old Bruce Anderson", who wrote the book on high performance 911s, (still an unchallenged book after ~20 years), and Steve Weiner, (both obviously on the take from Swepco),
, or a very small minority of owners who believe that synthetic works better w/ Porsche style synchros.
And with all due respect, Paul, with the amount and type of use that your car gets? It could probably have olive oil in the trans and you'd be fine.
