It's not rocket science Switch is 9th gen because it's a new platform succeeds a 8th gen platform yes it's that simple, X1X and PS4P were not new platforms they were versions of current platforms hence why they're not consider new gen platforms they didn't succeed the X1 and PS4.
We should just end the madness now and consider every variation to be a new generation. Congrats everyone, we made it to gen 35! Well done, especially you in the back! I've noticed how much hard work you've done, excellent job!