Before every race, there could be a 2 minute period where all riders perform a spindown on their trainers.
Not all trainers have spindown? Tacx Neo for example?
If tacx neo auto-calibrates than it wouldn’t need a spindown. Whatever the case, there has to be some way to feel confident in both sides of the w/kg equation if you want racing to take off. I recalibrate my trainer every n=8 rides or so, and, each time, I find my trainer has gone out of calibration and was reporting higher watts than I was actually putting out on the n-1 ride.
To do a spindown you need to warm up the trainer beforehand if it’s wheel-on. And the trainer’s own app is probably a better place to do it.
And two minutes before the start would be too late for anyone to resolve and sort of problem before the race starts.
I don’t see the merit here.