Firewall module not purging unmanaged rules

I'm using the firewall module as outlined in the PE quick start guide:

https://docs.puppetlabs.com/pe/latest/quick_start_firewall.html

It is working as expected, except if I add an iptables rule directly on the host it is not purged the next time puppet runs. Instead, I get the following warning:

Warning: /Stage[main]/Profile::Fw_base/Firewall[9001 0edc9f37593a5c39377db4c4ca0b34c9]: Firewall[RULE N] still depends on me – not purging

Where "RULE N" is the last rule defined in puppet. If I add 2 rules locally, I'll get two warnings referencing the last 2 rules defined in puppet.

I'm am using PE 2015.3 and have tested this with RHEL6 and RHEL7 nodes (same results).