For example, Federer's shorts are on TWE. TWE also has the "original" Nadal shorts, with the red dots and not the grey ones. So it has to be with Nike's decisions, not TW not wanting to carry them: they do want! They also have the orange and grey Vapor and CB, which are clay-only outsole, but that's more because Americans don't play on clay as much.
Although it's not written in stone. For example, the first Air Max Cages and Propulse 4 appeared first on TWE, then on TW. I'm not sure for the Cages, but I'm absolutely affirmative for the Propulse. Then, Babolat is a French brand, despite the Propulses being Roddick's signature shoe line. Still waiting for the new Cages colourways, or simply clay Cages since I mostly play on it.