Visual Studio on Mac isn't the same as on Windows. I don't know what you are using it for, but every time I have needed VS the mac version hasn't been enough and I have had to use the Windows version.

Yes iOS and macOS development requires macOS. This isn't really surprising. It's like how Windows development requires Windows and Linux development requires Linux.

Actually containing Unix code and adhering to Unix APIs and ABIs (which is what the standard is) are two very different things. If meeting some API requirements is all you need that's fine but you might as well call Linux and FreeBSD Unix too as they meet POSIX standards or close to it. Heck Windows was actually POSIX compliant at one point. Might as well call that Unix too.

As for that list article: Number 1,and 2 requires an application has been ported to macOS (you would know this if you actually read about and understand this stuff). An Numbers 3, 4, and 5 is just running Linux in a virtual machine and as a dual boot. I could run Windows or macOS applications on Linux using Wine and virtual machines, does that make Linux compatible with Windows and macOS? No.

6 is rebuilding a Linux project on mac which requires it to be source (and therefrom API) compatible.

Can I speak to someone who isn't condescending to people with more accurate information than them?