Let's take an example.
Honda NSX GT500 Base Model '08
Is this a race modified version of an NSX? No way.
It is a GT500 car without the livery. GT500 cars are built on spaceframes, and bear basically no mechanical resemblance to the road cars. The shell is made to look more or less like the road car it's "based" on, but will be modified as much as necessary to meet aero and regulatory requirements.
It's not an NSX, it simply looks like one for marketing purposes. The only way you'd ever modify an NSX into a GT500 NSX is by setting it on fire and starting from scratch.
So that one at least is not a Race Modified version. Some may be modifications of road cars, but I think you'll find a lot of the race cars are so far removed from the cars they're named after that they're really not the same in any sensible fashion.
Hence why I don't think it's fair to describe them as Race Modified. They're not modified, they're purpose built.