“I had to Google to figure out what “paper” they were referring to. Apparently they mean “instead of printing your email confirmation, you can show the hotel your confirmation in our app” which is pretty nonsense. Not the darkest pattern, but this obviously intentionally misleading.”
‹ All examples Booking.com 
Booking.com forces users to download an app in order to get “paperless confirmation”
“Booking.com asks if you want a ‘paperless’ hotel confirmation, which texts you a link to their app”