Black and white is not a practical solution for most things, flexibility is.
I run a lot of cars stock in the career mode where the bar is set so low.
That being said, some of them may require adjustment, like Final Gear (Tsukuba vs Fujii)
The beauty of Gran Turismo is that it provides entertainment for varying automotive tastes.
Different strokes for different folks as they say, I understand the motivation behind tuning.
It includes everyone from the novice trying to get an advantage on the AI in career races...
...to the seasoned racer in organized on-line racing trying to get a leg up on the competition.
Relying on PD programmers to deliver a "proper" representation of stock car can also be folly.
There are multiple documented instances of that in past & present GT series, they can make mistakes...
...they are human...and sometimes the tuners in the community can fix it, sometimes not.
You may prefer your coffee black, but the next person might like their's with cream & sugar...
...some even with an extra tune of whiskey.