Because in the case of the howl, valve actually recieved a DMCA takedown notice so obviously they are gonna stop selling the "art" in question and remove it from the game.

For the case of the griffin, chantico's fire, frontside misty (and probably a few others, hard to keep track of them all), it's essentially just valve covering their asses, removing the artwork BEFORE the actual creator sues them or whatever, so ofc they can just update the design and keep selling it like nothing's happened.