Upvoted because you're right about the actual heating effect, or lack thereof. However, that doesn't change the fact that heat is the stated reason that drivers are doing it, even if that's (a) only part of the reason, and (b) a superstition. Drivers, as with other sportsmen, can be very superstitious.
the current top crop of F1 drivers are remarkably un-superstitious. in particular the "playstation generation" which are remarkably competent professionals who have usually been extremely focused on performance since their early teens.
I would tend to believe that the swerving is mostly to feel the tyres and the car.
no no no, that's to warm up my arm and get my accuracy up. Same as why I mash buttons right before starting to play SC2. It's all science no superstitions.