Sorry, I was under the impression that a big reason for this argument was partially for the purpose of the Team Hawk Shuttle building.
Ish. It's more though for shuttles in general, which is what this classification is supposedly for. And it's a 60% good idea, classification purely on mass to orbit capability, same as we do for rockets.
For the hawk challenge, there's no restrictions on how you build the shuttle, size, payload, engines, parts, blueprint editing. As long as it goes up and comes back down again without breaking anything and you're not using exploits, same as with the rest of the challenges. I've part clipped and overlapped a lot of stuff on my entries rocket-wise.
Excaliber has a fair amount of it as well and no one has minded.
So yeah, I see even less point in just restricting shuttles, for hawk or in general.