Although it's unacceptable if people post uncredited recreations, this is certainly not an argument to halt the creativity of other people.
As you say, most good skin creators have one, therefor assuming the top poster wants to improve his arts this could just be what he needs. Redrawing the original game.png could also be a very useful exercise, but as the top poster has stated, would be too much work for little result. There's a good chance he wasn't aiming at the old teestyle in the first place, but only wanted a basic outline to work from. Considering there has never been a release of such premade file, you don't know if it actually will cause a flood of uncredited work. And when this flood would occur, the community has dealt with them before and made clear that the art in question was nothing but an uncredited remake. Developers and moderators will make sure these remakes don't stand a chance on the forum, or anywhere else for that matter.
The promotion of new artist has much more priority then defending the works already in existence. Legally they are open to the public anyway once they're published on the forum.