This looks like the same thing that happened in GTSport. Game comes out with only some tracks and cars completely rendered and in game. And the tracks and cars being still worked on come out as dlc during the game's life cycle.
Spa, le mans, autopolis, monza, calalunya, fuji, goodwood, red bull and laguna seca were all dlc tracks in gtsport.
Gt7 is folowing the same pattern as it comes out only with all gtsport tracks plus daytona, high speed ring, trial mountain and deep forest. And sometime later they start putting dlc tracks like watkins glen in game.
They probably have a ton of licences for tracks and cars, and as they finish rendering them, the cars and tracks go in game.