piranha1: Even though I use "-os windows" parameter when updating the manifest, for Stardew Valley, after recent version update, the script also downloaded a .pkg file, which seems to be a Mac version of the installer.
I guess that may be a wrong flag on GOG's side of things, and nothing you can do anything about?
(If anyone else had this happen to them: an easy workaround is adding "-skipfiles *.pkg" to a download command.)
The reason is that GOG has put an older 32-bit Mac version under extras, also with the Windows version. That's why it gets downloaded, quite correctly. The main Mac version is a newer version, I presume 64-bit version.
That's the case with some other games as well where GOG has, for a reason or another, put e.g. non-English versions under Extras (in which case they get downloaded even if you select to download only the English version), or also some Mac and Linux versions under Extras.
E,g, the original Planescape: Torment has fan-made Russian translations of Windows, Mac and Linux versions in the Extras, and Broken Sword: Director's Cut has the Mac and Linux versions of the original Broken Sword under Extras.
I recall at least earlier the idea for GOG was that they'd put unofficial/unsupported versions of games under Extras, like the aforementioned fan-translated Russian versions of Planescape: Torment. I guess the original Broken Sword isn't officially supported either due to the Director's Cut.