Well it was OutBound Only and this year they introduced InBound and I assume they still have to use Windows Firewall API like other software firewalls. You can read but they don't actually say: https://www.glasswire.com/best-firewall-software/
OK I see, a bit weird because the Windows Firewall has always managed both inbound and outbound access, but I guess you can now configure it. But it's still not a standalone firewall. In other words, if Windows Firewall gets bypassed, I assume you're still toast.
