The way I see it, this moves it in the right direction; one less place for the backend to have to care about the shader version. You could certainly argue for e.g. setting an appropriate write mask in the parser so that we don't have to care about the shader version here, and I'd be inclined to agree. I don't think that's an argument against this patch as such though.
That makes sense. I'd still prefer it in the parser, I think, but I can see how this is not moving in the wrong direction.