micktiegs_8: Possible scenarios are that
GOG is just sliding things under the rug and hoping nobody notices, or because developers don't quite like the reception from GOG they'll just abandon it.
For GOG to "slide things under the rug and hoping nobody notices", GOG would first have to be aware there is a new update or DLC or whatever that the GOG version is missing.
I would be surprised if GOG really was constantly tracking whether there are new updates to all the existing GOG games (even just those that can be expected to be still semi-actively updated by the developers), except for maybe some of the most important games in the catalog, whichever they may be. Heck, I am 100% sure Valve has even less idea what updates are supposed to come to all Steam games.
GOG is most probably expecting the developers to be proactive, ie. send them updates or at least notify of them, and not so that GOG has to constantly crosscheck against e.g. Steam versions whether there is any new stuff missing.
Unfortunately many publishers/developers don't seem to be so proactive, so sometimes someone has to bug them about it. Quite often it seems to be GOG users, but it seems many GOG games get updates also without our vigilance. As long as someone has noticed, many games seem to have received the missing parts after awhile.
For Valve it is easy because Steam is the biggest digital gaming store on PC, so it would be kinda unthinkable there would be an update or new DLC for some PC game but the Steam version would be lacking behind. Unless it is one of those old classics that first appeared on GOG, and GOG has made their own fixes to them.
BKGaming: They also said soon developers will be able to push out updates themselves like they do on Steam, so we should get updates faster, and so if we don't get an update after than then it's the dev's fault in my view. They are rolling this out to developers slowly.
Do you reckon that includes also the offline installers? Will the developers maintain them too?
Or then GOG will change they way "offline installers" are distributed, ie. they are something you get through the Galaxy installation (like the installed files compressed together, and some script which adds any dependencies etc.), not a proper installer anymore. Depending what kind of solution it would be, either I would be fine with it, or not.
BKGaming: On GOG they have to contact GOG, wait for them to test it and package it, etc. GOG gets between them and their customers.
And as a customer who uses offline installers, I've liked this approach so far, over e.g. the Humble Bundle approach where the installers are a messy pile of files that the publisher has slapped together without any rules.