They are just asking a question. They haven't said that's what they are adding.
If they can do this M1, then they can also do a normal street version and the Pro version.
The fact they are asking means they are considering adding it.
And you have a point in that they can also do normal street version and the Pro version M1's, but BMW lacks the kind of support Nissan and Mazda have. I am under the impression that if this car makes the cut and does get developed for this game we will see the same kind of one off development we have seen demonstrated repeatedly in Gran Turismo with Cars like the GT-40, McClaren F-1 GTR, Vertigo Race Car, Lister V-12 and so on.
Curiosity killed the cat right so I should have learned something since I know the saying, but here it goes anyway. How much can something like this really "bother" someone? And why? It is still just a M1 underneath. And the game is light on some great driving Bimmers.
From where I'm sitting it looks like they are making the same mistakes over again. A thought process from the recent smurfs movie comes to mind here, they are giving us what we ask for and not what we want. Yeah, we ask for more cars...but why give us cars like this. To be honest I'd be happier if they took the lazy road and took a dozen or so race cars we already have and gave them a couple two, three unique liveries be they existing or not as opposed to one or two one off cars. I want more options not optionless cars.
This brings to mind an interesting little factoid. The fifteenth art car, we have an existing body render for it in GT-5. The fifteenth was painted on a BMW V-12 LMR...(Ironically, it literally says "Protect me from what I want" but still)
So...Why the Warhol one and not this one, or then again a question I can assume the answer to, why just the Warhol one and not all 17 of them?