I've driven year-around on MPSO tires for years. Daily driven. In temps down to 0. It's fine.Someone in a warmer climate check their tire sidewalls and see if there are any micro-cracks ... bet there are.
Cracks happened 15-20 years ago with those shit Mercedes Original Pirelli MPSO tires from the S197s. The tire tech has gotten better, specifically the Michelin PS4s. And it's not the sidewalls, it's in-between the tread blocks where cracks can appear.