ThoRn: About time GOG! Why are yall so late with the DLC for this game compared to the Steam version of it? Anyways, I just bought both of them and have been waiting "for-ev-er, for-ev-er, for-ev-er" (reference for the movie "The Sandlot")
Question:
Do you even know how any store selling 3rd party products, even works?
Answer:
You clearly haven't got the slightest clue.
GOG is curated, unlike Steam, but that only means GOG approves specific Publishers, or (rarely) Games to be released on the store.
In both cases, on Steam, and/or GOG, it is the publisher of the game that decides;
1 When content is released on each store
2 At what price that content is sold for at all times.
No store has any say in the release timing of content, unless they have made an exclusivity deal.
Even that doesn't set the release date on that store, it just sets the length of the exclusivity period will last for, AFTER release.
No store ever decides when content will get released on the store, that's the publisher's decision.