I wrote to them about a bug I'm experiencing on Mac which has been written about elsewhere on this forum by others (in which once you set your engines to full speed, your ship will blow up over and over again for the rest of the game, even if the engine is at normal temperature, even if you completely stop or dock somewhere). I got a response back telling me that I am playing an old version and should update. Had to write back to tell them that no, there is no update higher than mine on GOG. Then got a reply basically saying "oops, guess we didn't upload it. I'll see if I can get the new version to GOG." Seems odd that they had forgotten to upload the newest version to this platform. Wonder how long it has been sitting there, done, without being uploaded to us. Will see how long it actually takes to arrive.

What's odd is that I can find no reference at all to version 2.2.5.3148 outside of the Mac version here on GOG. Before I saw your post I was tending toward the idea that 2.2.6.3150 just fixed some Windows/Linux specific things that didn't need to be touched on Mac, but now I'm less certain.

edit: Seems at one point the Mac version was (at least "on paper") 2.2.6.3150 but then was reverted
https://www.gogdb.org/product/1421064427#changelog

Last night I had another interaction with Failbetter and they got the new version uploaded. Sounds like they might have had some difficulty getting the update posted through GOG. But mine has now updated through GOG Galaxy and the bug I described seems to be fixed.