I'm not a dev, so I don't know entirely how this mess all works.

I would guess....they would have to test the game to work for different platforms; and w/ all of the main platforms running (Steam, GOG Galaxy, or whatever) or whatever else is running in the background.

We've had games w/ either specific issues to each platform before - b/c it has all of this mess (client-app programs) running in the background with their own features.

i.e. Wizardry 8 never worked on the Steam-version for me b/c it doesn't like where it's installed and really needs C:\WIZ8 for that version, so I have to run it outside of Steam from the EXE just to boot it.

IIRC, Dying Light has Steamworks support on Steam; and GOG Galaxy Support on Galaxy - which means there's probably at least 2 versions of this game, both with their own different versions and toolsets used for each platform. This was the only nice thing about stuff like GameSpy (when it was up), as....well, dev's could use Middleware to just have different versions everywhere for players to do MP.

I would guess they'd have to make different versions too - i.e. Steam-version has to use Steam-stuff (even more so true with the game there used CEG - for Steam Achievements, Steam Cloud Sync, Steamworks for Multiplayer); and GOG version has to use Galaxy stuff for Cloud Sync & Galaxy MP (if this game supports MP over there).

This, of course, gives more reason - especially when games get old and eventually show-up on GOG - that they should get rid of CEG/Steamworks DRM wrapped around EXE by then. By the time a game's old and everybody owns it on Steam or GOG, it's a waste. Less for them to test and can make it easier to have to change less stuff, once they un-wrap the EXE from any annoying client-app DRM.

I don't know if they could "comment code out" for each version (i.e. when using C, you can lazily comment code out so it doesn't use it, especially if there's tons of code there); or write code to detect if you're using either Steam or GOG version also; or if they just create different versions for each platform to utilize specific toolsets - i.e. Steam has Steam-works; GOG has Galaxy.

This is why I think games sgould just have in-game Achievements done that way - and when players Achieve something, it's done in game...and THEN uploads to the appropriate servers depending on what version you have (i.e. it detects if you have a GOG Version or Steam Version).

Regardless - yes, games should be always kept up-to-date, on all platforms...but likely, this ain't going to be the easiest thing for them to Achieve, depending on what each version entails, in terms of extra mess for Achievements, Cloud Sync, Multiplayer Suite, etc...b/c Steam and GOG each have their own Suites of stuff now.