To be fair, I almost never come across tar files. Most crossplatform software provides .tar.gz for Linux/macOS and .zip for Windows.
Should windows have native support for tar.gz files? Maybe! Maybe not. I dunno. So when I come across something using that format for windows what it really comes across is half-ass Windows support. Which isn’t the end of the world. But it’s rarely a good sign.
Ah, yeah, that's completely fair. If someone is making an archive _for Windows users_, that archive should absolutely be a zip. A tarball definitely sends the signal that Windows users aren't the primary audience. Sometimes that's okay, sometimes it's a sign of a really shoddy port.
Sort of. I wouldn't make a separate source archive for Windows users - anyone who can compile stuff will manage installing 7-Zip or another archiver that handles .tar and solid compression wastes less space and bandwith. For Windows-specific archives .zip is a no brainer though.
Technicall yes, but if you care about user experience you should treat it as a single compressed archive not as one archive in another like e.g. 7-Zip does.
Should windows have native support for tar.gz files? Maybe! Maybe not. I dunno. So when I come across something using that format for windows what it really comes across is half-ass Windows support. Which isn’t the end of the world. But it’s rarely a good sign.