If you must level the pan and not the truck, how in the world do tranny shops get the pan level on the lift? Leveling the transmission pan on a 8HP70 in a RAM requires the rear of the truck to be elevated by about 12", which can't be accomplished on a lift. It can only be accomplished on the ground with jackstands.
Given that the 8HP70 trans is used in various vehicles (BMW, Jaguar, Jeep, Ram, Rolls-Royce, Masserati, Dodge, Volkswagen, Aston Martin) each with their own driveline angle, I agree with you that the fluid fill procedure is specific to the trans not the vehicle, therefore forcing the trans to be level upon proper filling.
A few notes from around the web:
These guys kept their vehicle level:
1. https://www.youtube.com/watch?v=mNo9Ln5KrOE (Boosted MotorSports)
2. https://www.youtube.com/watch?v=bueSenZlKm0 (JWC Motor Sports)
3. https://www.youtube.com/watch?v=O6caRGWhQdk
4. https://www.youtube.com/watch?v=TIZkFxmcClY
5. https://www.youtube.com/watch?v=4eWnnNdoFoE (BMW leveled vehicle)
6. https://www.youtube.com/watch?v=_qJ1iq0Eb-8
7. https://www.youtube.com/watch?v=BPkCUfqi-gE (Chrysler 300C)
These guys raised their rear-end and leveled the trans pan:
1. https://www.youtube.com/watch?v=AqbLqjQvA5E
2. https://www.youtube.com/watch?v=-e06ekxxZkE
I'm still confused. I'll keep looking/researching.