I'm not a believer in this "cold tyre" theory.
It's never something I've experienced, or at least "blamed" as the reason why I've I've had a bad first lap, either from race start or pit lane.
To my mind, if it was actually true, it would be something I would continually experience, essentially without fail, every race/practise.
And it's something I almost never "experience", and nowhere near consistent enough for me.
I can tell you it takes the better part of 4 minutes sitting idly in pit lane before there is the slightest colour indication that the tyres are getting cold.
As for turn one incidents, it would seem to me that the better explanation is that people simply don't know where to brake.
For the majority of racers, every race start is a different grid position.
This means you approach the turn 1 braking point at continually varying speeds.
Essentially everyone has to guess when to start braking.
It isn't something you can really practise.
Some brake too early, causing accidents, and some brake too late, causing accidents.
This seems a far better reason as to why turn 1 can get ugly.
And ignoring that and blaming it on cold tyres instead seems a stretch to me.