What makes you think the (player facing) GTS alignment settings are the values used by the physics engine? It is quite possible the shown values to the users are offsets, chosen to simplify the presentation of tuning to not confuse novice players.
I do agree it would be nice to have the actual measurements, but it can't be assumed.
Given that the cars in GTS drive quite realistically and differently I would think every car has unique alignment settings close to their stock alignment from factory. That is what PD do, I don't think it's fair to assume they 'wing' stuff like this without research.
While it's true we don't know what are the actual values of the unit-less tuning parameters (ARB, damper, downforce, LSD and to an extent brake bias), you can clearly see from the pattern that every single car comes with 7/4 ARB and +0.60 rear toe. Now the 7/4 might "hide" some true number underneath, but it's highly unlikely an F150 Raptor (front heavy) and a 911 Turbo (rear heavy) would share the same ratio no? And +0.60 rear toe is just asinine. No production road car will have such an aggressive amount - it would kill rear tyre life considerably.
That's just the obvious problem. If you follow the Time Trial thread and the tunes being posted, I've seen wildly opposite values produce remarkably similar laptimes and similar driving feel. GT's tuning has always been trial & error, filled with quirks and exploits not based on reality. I mean to fix understeer, the ideal setup is max front ride height, min rear
Downforce is another well documented issue. If you test the top speed of most super/hypercars on SSRX you will find they are almost never accurate. McLaren F1 is notorious for being much slower in the game than real life. PD had to add so much body downforce, because the physics engine doesn't calculate underbody downforce enough (the real car has fans on the rear flanks to help the rear stay planted under braking). The LaFerrari on the other hand is so much faster in game, because PD doesn't give enough downforce (which also makes it handle like crap). Most supercars have 100 rear downforce with none on the front to balance it, which makes them super understeery at high speeds (e.g. 458 Italia daily race at Maggiore last week - despite the Italia having that "whisker" flaps on the front bumper specifically to create downforce).
I could go on and on. The fact is, most of the cars in GT have always handled a bit off compared to their real life counterparts. If you mess around with the settings a bit they can get close, but default tune are just wrong most times. Sure some cars are closer to their real counterparts than others, but that's just a probability thing. When you have 400 cars covering everything from 500F to F1, some cars in the middle of the normal curve are going to feel pretty "ok". But that doesn't mean everything is correct.
