I'd assume it's fine as long as they're marked as such. If anything I find them preferable to photomode shots, as they're at least not completely non-representative of how the games actually look.
That said, you could make the argument that at this point they cease to be "console screenshots", much like emulator shots wouldn't be.
Well almost all of the pics in this thread are from photo mode that enhance the visuals, for me it's kinda like cheating so I can't be too impressed from this.
Though, the game does look beautiful during gameplay, probably the best looking racer, especially under rain, but not that good looking like those pics suggesting.