Like you I was used to having the DSG serviced every 40,000 in my MK5 so was surprised when the dealer mentioned it was 80,000 in my PP.
If that's what they are saying I'll probably go with that.
I would. Essentially they’re either saying that
-It’s very unlikely to fail ( and experience has shown that, so let’s increase the service interval)
Or
-Changing the oil makes no difference to whether it does or not.
Interestingly, my 1988 205 GTi service handbook states , for gearbox oil - “ no oil change “
They probably didn’t expect the car to survive 30 years when they wrote that handbook, so I changed the oil last year!