More correctly, the title could end "unless you only ever target Win32 on x86". Shipping software that's at all portable across operating systems and architectures, that's a different story.
Nah, even for that. I don't know what gp is on. I recently downloaded a project a friend made on rpgmaker. I had to manually download rpgmaker itself, a dll and a new font. It wasn't a complex project, he isn't even a developer, he mostly make illustrations and graphical assets. It was really, really basic stuff.
That said, I have almost 10 .exe that just work and that I take from computer to computer since 2015, like I have around 30 .sh/.py/.lisp that i do too. Being charitable, I think GP just have a lot of scripts/small tools that just work, and he was referring to that.
The majority of desktop users, perhaps. Most users are going to be customers of a system that likely runs “in the cloud" and that means, by far, Linux.
