Steam version says 1.1, whereas GOG latest is test-5 is the download area, 0941 as the game launches.

Is this a case of GOG customers getting the short end of the stick?

I've asked in game Discord server cause I noticed the strange version name too.

GOG version is 9041 (named test-5 - manual updated cause some issues)
Steam version is 9119

A programmer (or "the programmer", IDK) said that the difference is only 1 very minor non-gameplay change (DLC was left enabled by default for testing purposes), and 9041-9119 are actually the same version.

In the game Discord server there's a channel with all current versions on each Platform.
In non-PC platforms there's a parallel "Platform Version" numbered 1.something (but not on GOG or Steam).

There's also a channel with all the change-logs (very appreciable IMO), with also "unstable steam builds".

Apologies for the exceptionally slow reply, just wanted to make sure that we're clear on this.

test-5 was indeed the same version as on Steam. Due to an issue with our build pipeline I had to manually upload new versions (and name them, as you can see I'm very original with my naming conventions). This only became a problem last week when an update broke the DLC, so we spent this morning fixing it so that it once again automatically updates builds to GOG at the same time as Steam.

GOG and Steam will pretty much be on the same version (unless I'm testing something that's platform dependent), consoles will lag behind a bit because the patching process takes a long time. We also have to use different versioning there because the consoles enforce certain versioning, but the in-game version number is what we actually use.