I don't see any difference, hook is not triggered after firewall-cmd --reload.
Reading the https://www.libvirt.org/hooks.html#location
/etc/libvirt/hooks/network
Executed when a network is started or stopped or an interface is
plugged/unplugged to/from the network <-- this doesn't seem to
be exactly what is needed as no such events occur.
At this point systemctl restart libvirtd will trigger
/etc/libvirt/hooks/network and insert the desired rules which I
think is strange because there is /etc/libvirt/hooks/daemon for
this.