Treadlight: [...] If they are simply not here, I guess I should go yell at Motion Twin about this.
That is probably
exactly what you would have to do.
Now about those updates: It is my understanding that those versions of the game are highly experimental and aimed at people who don't mind losing their savegames because of incompatibilities with later full updates. They are more like versions for testers than for customers. I'm not suggesting you wouldn't like them but I would like to point that possibility out.
In their
Development FAQ, they wrote:
Treadlight: How often do you expect to release updates? Initially we were working weekends and nights to push out an update every two weeks, then we realized that that this kind of behavior get you divorced, so we’ve slowed things down a bit. Now you should expect major updates, with new levels and new stuff every two months or so
So I wouldn't expect any bigger updates until the end of February or so.
As to
why we don't get them on GOG: It might be GOG's decision to not have products that reflect badly on the quality of their games. It might be worth asking GOG's support team about that. It's also entirely possible that
Motion Twin don't want to put in all the work of removing the Steam modules on every daily build the push onto Steam.
If get any good results by poking those two please consider sharing them here.
Oh, and if you get their attention for a hot second maybe remind them that they have a subforum on gog.com as well, so next time the devs can try and answer your questions themselves. ;)
Either way, I wish you all the very best!