PS3 was also selling and had new games (several crossgen as well) for over 2 years after PS4 released. TLOU and GT6 launched only on PS3 at the time and one of then was even after PS4 was launched basically.
The number of double dips isn't that much either, and if Pro didn't exist most would have bought vanila. Much more likely that a household have 2 or more switches due to portability and starting at lower price than another PS4 just because of Pro.
"The number of double dips isn't that much either"
How do we know this?
What does that matter? Should we not count Sales of Pokemon versions because a large amount of people buy multiple versions? Is my purchase of Yellow version invalidated because I owned Red?
Certainly wouldn't be useless information.