StingingVelvet: There has to be a reason games like Control go to Steam a short bit ahead of GOG. It's not DRM either, because Control was DRM free on the Epic Store a year ago. Perhaps they're just focused on getting the Steam version out the door and GOG is understandable a secondary concern, or perhaps they have a deal with Steam for front page promotion. Who knows. At least with Control we knew it was coming, others like Greedfall you don't.
Though lately it is pretty easy to guess which games might come here quickly depending on the publisher. EA, Ubisoft? No chance. 2K? Maybe. Focus Home Interactive or THQ? Probably.
I believe it's something to do with how Steam's "popular games" algorithm works and devs (whether correctly or incorrectly) think that they will chart higher if they try and concentrate all their sales on Steam around the initial release. If they release on GOG at the same time there are probably some customers that could go either way. By denying GOG the "launch buzz", those floating customers will go for Steam. GOG is left to mop up the die-hard anti-DRM folks and some of the late buyers.