⬆️ Kirk's answer is the TL;DR, but I wrote this as he replied:
Because Microsoft ended support for Windows 7, we no longer test Photo Mechanic on that operating system. It is certainly possible that Photo Mechanic will continue to work correctly (I don't think we have made any changes that rely on new features of W8, 10, or 11), we just can't guarantee that it will continue to correctly, since Microsoft does not guarantee that the OS will work correctly. If you aren't encountering any issues with the current build, I don't think you need to downgrade, technically the readme has said it required Windows 8 since August or maybe even builds before that, I think the template for the forum post just got updated for this build.