That is part of it, also they didn't roll over on the sidewalls and physically look like they have more tread depth on them.
These have done 5 track days on the rear of the car and 5-6 on the front, plus a deca or two. 32-34 PSI.
The other pair are 5 track days newer, the 4 combine did a 1.25.98 at Sandown couple of weeks ago.