07 Touring - "puffy" armrest cover

[Isresistancefutile?]

The center armrest cushion in my 07 Touring seems to inflate a bit under warm direct sun. While parked for a while today with the temp above 60, it puffed up again like a little balloon. Without measuring, I would say it swells up by about an inch in the center, and goes right back down again at night or when the interior cools down.

Has anyone else experienced this? Interiors in the Touring are all black, but I'm interested to know if others with light colors have seen it. I'm filing a warranty claim anyway but would like to know what to expect to hear from the service writer (ie: "they all do that").