Real cause of "rivering" or cupping? Air pressure?

Good advice from Bikeboy57. If you are passing through a high elevation area then no need to adjust the tire pressure. The tires will handle the tire pressure just fine. How many millions of commercial vehicles never adjust tire pressure and they travel?

For extended stays at a significantly different elevation then adjust the air pressure.

OP Elevation changes don't explain that one tires higher pressure. Was it in the sun or otherwise warmer? Doesn't seem likely that the tire wear was the cause but???