I just laugh about the denial related to the field being planted on sand. There are photos and purdue.edu articles explaining the installation of the PAT system and the sand base that it relies upon. A 90 second google search brings it all up.
Not hard to see that there have been issues in the past that have caused them to explore new solutions.
An early season night game (looks like ND) where you can already see the wear.
Here's the sinkhole from 4-5 years ago where you see all the sand that is the turf's underpinning.