Really hard, if not impossible, to help you without seeing your firewall rules on WLAN.
But there is something to this. It is the combination of both the pass NAT rule and NAT reflection (which is also enabled on the port forward installed by the package).
# NAT Inbound Redirects
rdr pass on re0 proto tcp from any to 10.10.10.1 port 80 -> 127.0.0.1 port 8081
# Reflection redirect
rdr pass on { re2 enc0 openvpn } proto tcp from any to 10.10.10.1 port 80 -> 127.0.0.1 port 8081
rdr pass on re0 proto tcp from any to 10.10.10.1 port 443 -> 127.0.0.1 port 8443
# Reflection redirect
rdr pass on { re2 enc0 openvpn } proto tcp from any to 10.10.10.1 port 443 -> 127.0.0.1 port 8443
re0 is LAN, re2 is OPT1
OPT1 has no rules on it. Can access 10.10.10.1 on 80 and 443. Because the traffic is passed by the port forward.
The ruleset is just doing what it has been told to do.
This is not a NAT issue but a pfBlockerNG issue. Moving there.