Correct.
Also TAC confirmed this option is only related to multi-portal traffic.
So if option 1 is enabled, malicious http/https traffic sourced from an external source IP destined to a gateway external IP portal URL will be dropped by explicit drop rules, all other http/https multi-portal traffic will be allowed by implied rule, before the last explicit drop rule (explicit cleanup).
My other concern is still allowing SSL VPN traffic whereby the user is connecting using a client (not multi-portal traffic), but dropping malicious connections to gateway external IPs on http/https that are currently being accepted by implied rule.
Is SSL VPN traffic whereby the user is connecting using a client caught by a different implied rule, in which case it should be unaffected? This SSL VPN client traffic is https, though TAC mentioned this could also be port 4500 which I've never seen (port 4500 generally used NAT traversal in IPSEC VPN).
Or is this traffic not caught by a separate implied rule, and I will need to ensure I explicitly allow this traffic?