Well good to know it's not for mac or anything weird like that, but my issue still stands. I haven't published a game on Itch before so correct me if I'm wrong, but I believe you're able to specify platforms on a per-download basis. Just mark "PvZ in GML Release v0.1.0 - Download.zip" as being for Windows and people will be able to install it via the Itch app just fine. For some reason, if the creator does NOT specify the platform for the download, even if it's the only download option available, the Itch app literally won't let you even select it. It's a pain sometimes.