They're intentionally trying to drive people to buy from their service rather than a competitor's through innuendo. As far as I can tell GMG is a totally legitimate site.
Except that the game is also digitally available through Steam, Origin, Uplay, Humble, Gamespot, Amazon, and probably plenty of other outlets. So I don't necessarily buy that as the reason CDPR decided not to sell through GMG.
GMG is a legit site. Its a legit site exactly because it only deals with product directly from publishers. The reason they are in this mess is because they decided to act more like a cdkey reseller, and decided not to tell anyone.
Like someone else mentioned, everyone involved (Gamespot, GOg, GMG) are coming out of this with stink on their faces.