It's a videogame, it's not an error that one would commit in real life racing, it's purely isolated to the videogame environment.
It's my understanding that this thread is about eliminating a "game-ified" aspect of GT7.
More to the point about videogames, it VERY VERY VERY poor form in games to have an input be ignored. They should either give you an audible sign and tactile feedback (vibration) that you messed up the downshift, or (what's already in the game) damage the engine, thereby throwing the lap out the window anyway.
All the examples given of downshift protection are from cars with electronic aids. GT has an enormous selection of cars that do not have any such electronics. The game emulates the speed of the gearbox on a per case basis, different cars, different box types, so it's very necessary to give the player feedback.
As it stands now, I really do dislike the guessing game of whether I get a downshift or not. I used the example of the Super Formula. With that, enter a corner, hit the brakes, and downshift as fast as you can possible manage. Switch to the F3500 (which should have a sequential semi-auto), and the shift pace changes. Switch the Ferrari F40 as an example, and it changes again.
Now, I like the differences, but it feels broken to call for a shift and get nothing. Not even an "clunk" or gear grind sound to tell you what happened.
And remember, in real life, with a proper manual box (which is what many of the car in game are supposed to have), you can try to jam the gear level into the gear, but it won't go until the gears line up. You get a crunch when you try (and a giant repair bill if you succeed). So, IRL, you get feedback. In the game, you should get feedback too.