I wouldn't say its common, but it happens. I have a 2014 with no ripple. I put a high quality 3M Crystalline on windshield (70%) to reduce heat and UV damage along with proper annual leather treatments.
That said, the cars you are looking at regardless of mileage might have been parked outside in direct sunlight and not sure what area of country they were in?
The warranty would depend on how bad and dealer discretion ... certainly worth an ask.