Donk
Piss Artist Formerly Known As OllieNZ
Maybe the bias tires are different?
Heat cycles causing the tire to harden sounds like the manufacturer playing games to sell tires
It's certainly legit for race slicks. I'm an F1 fan so I'll use them as an example. Their soft compound tyres are normally good for around 10 laps from new, but if they start the race on the set they qualified on they'll typically get an extra 5 laps or so + the 3 laps they do for quali out of them due the the quali heat cycle (warm up lap - hot lap - cool down lap).
IIRC It's to do with how they cure the stickies. Race temps are hotter than the cure temp which effectively "post cures" the tyre making the rubber harder. To get the rubber to soften like a new one you'd have to get the tyre temps even hotter again which may not even be possible on the car.