If developers can't be arsed to mention on front page what platforms their product supports then I don't think they really know what "intuitive" means. They might be cool guys and nice people and all but interacting with users is not their strength.
It's also not a bad exercise for Windows and Mac users to learn that the best way to determine this is to go to the downloads section and/or look for system requirements.
Of course with modern versions of Windows you can probably run this program through WSL relatively easily as well, but that is far from the default for running open source programs.
As this is GTK based, I suppose there's no technical reason why it can't be made to work cross platform if someone would put in the effort. It'd still be nice to see it mentioned, though.
Then I started thinking: "Well, their are probably not malicious or ignorant. This is just probably an acceptable behavior." And continued to behave that way.
I don't think we should complain when FLOSS non-multiplatform software (that support a FLOSS OS) should be criticized when announced without disclosing the lack of portability. People who choose to not use a FLOSS OS should be able to try it more easily and without the limits imposed by usual proprietary software licenses restrictions.
Now, if you announce something, even if it is FLOSS, that only works on windows or macos, the thing is entirely different. A FLOSS user will have difficulty trying it or will have to agree with the restrictions of proprietary software licenses. These are the software that, when announced, should state very clear which platforms it supports.
Wine runs lots of stuff very well.
But I also understand that the true beauty of open source is the entitlement of free work from devs on a project receiving less than 8 euros a month from donations.
Someone posted the project to Hacker News. A commenter pointed out that they didn't put the supported platforms on their website. That has nothing to do with "entitlement of free work". If the devs don't want anyone else discussing their work, they have every right to keep it private. If it gets posted to HN, it will be discussed.
This is entitlement to free work. Raising an issue is much more reasonable than an HN user submitting a change on behalf of another random HN user. I do understand that the OP wasn't asking for someone to do this for them, though, and not displaying supported OSes is a totally valid critique.
That said, the download page is where I'd definitely expect something like this, and the download page is useless. It tells you that various Linux distros have Pitivi in their package managers (which ones? links?), and has a Flatpak download (what's flatpak?)