My version of Biomutant updated automatically to the first patch via Galaxy. I think this happened on the very day the patch was released elsewhere (thanks to the devs for remembering GOG customers!)
I think this might simply be a matter of miscommunication: The devs refer to the patch as 1.4 for some reason. The GOG Galaxy update history as well as the offline installers are listed as 1.1, but the patch log is identical to the patch log of 1.4. I can also confirm that my installed GOG 1.1 version of Biomutant has all the features listed in the patch log, so 1.1 on GOG is version 1.4.