The chances that anyone having this problem didn't reboot their system seems low to me. I probably rebooted a half dozen times. At first I thought the problem was that Parallels lost connectivity to the Mac, so I also rebooted the Mac multiple times and then the Windows VM. If there is a micro update at Windows VM boot time, it doesn't fix the problems described in this thread. It was on a whim that I finally removed the firewall component.
What you are implying is that a person rebooted only once, after they uninstalled the firewall. That's possible... seems unlikely but possible.
Also, the people posting here including me observed numerous bugs in turning the firewall on or off. On some screens it could not only not be turned on (for instance, the Alerts screen which always said it was off regardless of Settings), but also when they tried to turn it on it reported "Firewall not available." So, turning it on and off, which everyone tried, is a futile endevaor.
Anyway, that's the situation in this thread. Other threads are reporting other problems, like rules not being learned or being learned and then forgotten.
But - that said, I'm just frustrated, and actually do appreciate the efforts by several of you to offer suggestions! You don't have to do so, so thank you for chiming in.