MoCA would require a PoE filter on the incoming line so the MoCA signal does not "escape" onto the outside line and cause interference with other cable subscribers on the same line. The only "security" issue with MoCA would be such a filter has not been installed. I find it hard to believe the Wifi Gateway doesn't have a PoE filter built-in to address this. The lack of PoE filter install is the only practical "MoCA" reason the feature is automatically being disabled.
Here is how you can side-step the MoCA feature of your modem with another MoCA adapter. MoCA adapters typically have two coax connections and ethernet; one for passthrough and the other for connecting other MoCA devices. You can always try something like this ...
incoming coax --> moca coax port | moca adapter | passthrough coax port --> cable modem --> router
... then plug moca adapter ethernet into one of the network client ethernet ports on the router.
Your cable modem will send/receive signals through the passthrough coax port. Internal network traffic will flow through the router. With the MoCA adapter connected to the router via ethernet, internal network traffic will flow through the MoCA adapter to other MoCA devices. At first it seems counter-intuitive and circular but signals are separate and don't interfere with each other.
Don't forget... you'll need to install a MoCA PoE filter on the coax line in from the outside. Otherwise, the cable company will track you down ;-)