Previous Forza games changed ToD during the race too but that was backed not dynamic.
Play GT5, GT6 or pCARs 2 to see what means dynamic.
That doesn't means it is dynamic lol
I've played (and own) all of the games you mentioned other than PCars 2 (I have the original though). You seem to have no idea what you're talking about to be frank.
Forza Motorsport 1 had day racing and night racing, but never transitioned during a race.
Forza Motorsport 2 through 5 didn't even have night racing.
Forza Motorsport 6 brought night racing back, and added wet weather. There are no transitions however, you pick day or night, wet or dry at the start of the race, and whatever conditions you begin the race with are the same you end the race with.
All of these are static conditions.
Forza Motorsport 7 allows for races to begin and end at different times of day, and allows for rain to start and stop during a race. This is dynamic...
It doesn't allow the player to freely set the conditions, and it doesn't allow these conditions on all courses, but that doesn't prevent it being dynamic where it is used. This is a ridiculous point to be arguing against.