Lyumao: Yeah that's possible and in one sense it's prety enjoyable.
But i'm realy curious (not for this game only but also with other games that haves these kinds of situations):
What's the difference between:
Release an update for Steam and release an update for GOG ?
Assuming there are no worries (bugs/crashes and others things like that).
What's the difference between theses two plateforms from a point of view game development ?
That can be interesting ^^
Spectrum_Legacy: There is not much of a difference I believe, it's more like doing more of the same-ish all over again. Some things like fixes you can port easily, while others require intensive testing under specific conditions to make sure the desired functionality is maintained. Sometimes changing a small thing in your core build breaks a lot of added features down the line.
Easiest example would be a completely drmfree build, like some sort of internal version you build and develop upon. It's easiest to maintain since it doesn't have any 3rd party extras attached. Then you can have an extension that builds upon it that has steam features implement, another build with gog features implemented, and so on for other platforms. Or you have one version with both of them (that's why you sometimes end up with steamworks dll files in gog install and vice versa - it's kinda easier to have just one build for both platforms imo, for sake of simplicity and you could deliver updates almost at the same time).
However even despite that, there is windows, linux and mac build on top of it and each time you publish a major branch update that you think is ready to go, it has to go through quality assurance and testing before going live (if you are responsible dev and who can afford the qa service that is). It all takes time. Lastly, both steam and gog takes time to validate the update. That can range from almost seamless upload (couple of minutes/hours) to a week or two in some rare cases. I don't have a direct comparison experience between steam and gog publishing, but I believe that steam has it more streamlined and thanks to the size of its userbase is seen as a priority.
In case of this game, I believe there were some bugs reported by steam users (not sure about consoles). I don't want to speak for devs here, but it seems they went the route of first fixing all the issues internally after steam users helped to "test" the patch and only then delivering a single finalised update on gog, instead of going the multiple patches/QA sessions on each platform/OS route. However it's worth to note that the gog version might end up having its own platform-specific bugs too, which we will have to "test" ourselves.