So I bought this on GoG in good faith the developer will update this version of the game just as often as the steam one. I have run into problems in the past where versions of GoG and steam games have had mismatched versions and thus if you play with friends across platforms it can cause troubles.

I realize this is not multiplayer yet, but the dev is just weeks away from creating multiplayer it seems.

The only GOG game that exists: The Witcher 3: Wild Hunt.

Well to name one that I had to refund because of the mentioned above, Windward. I think he is doing better now but in the past he would update the GoG version like a day later.

To name one? You're opening post makes it sound like you're talking about a game in particular

I'd guess stardew valley, from what I hear there's multiplayer incoming in some time.

Unfortunately there are quite a number of developers/publishers that do just that, release their game both on Steam and GOG, then never update the game on GOG either ever, or for a very very long time, sometimes without saying a word ever about it, other times making promises they never keep or take unacceptable amounts of time to provide updates for.

It is a sad fact that some publishers very much do consider GOG a 2nd or even 3rd class citizen and just straight out don't seem to give a shit. At best they fire up the excuse train of only having a small team of developers blah blah blah. It's just pure bad planning, organization and project management in the end IMHO.

What's worse is that GOG lets them get away with it for months if not years on end without pulling their game(s) from the store, and it isn't clear if GOG puts a flamethrower under their asses or not.

There is a thread somewhere in the forums that tracks games and their publishers/developers that treat GOG customers as second class citizens. IMHO, it is a good idea to boycott those games unless the developers are completely transparent about it and seem to be honest and trustworthy albeit perhaps with poor management skills. Even though it is inexcusable, if they're honest about it and do give a vibe that they will indeed come through, in some cases giving them a bit of slack might be in order so long as they do in fact come through. If it is a multiplayer game and being out of sync with the rest of the world screws over GOG players though, then I would say boycott the game completely.

We need a higher standard here than just getting leftovers thrown over the fence "as-is" and broken.

There are developers on GOG that will release the updates only a mere day or two after the update was spawned upon Steam; that is acceptable. What is NOT acceptable is having said developer badmouth the GOG version, instilling a lack of trust in that developer. For example, I'm not buying Lovely Planet or whatever it's called, not after when the developer claimed the GOG version was 'inferior'. In fact, do yourself a favor and DON'T buy from these developers at all, anywhere. If they promise something, they better deliver on it instead of running away.

We have been waiting for the promised VHelsing Final for 7 months now following the Steam release. WE are however lucky enough to get the vastly overpaid skin DLC for Dying Light on nearly day 1 - so it swings in roundabouts I suppose.

Yep, that thread is indeed very handy:

https://www.gog.com/forum/general/suggestions_wanted_for_gog_mix_games_that_treat_gog_customers_as_second_class_citizens/page1