Where is the "allowguest" variable?

I know “allowguest” is a variable in sip.conf, but it’s setting doesn’t show up in any of the included files within sip.conf (sip_general_additional.conf, sip_additional.conf, etc.). I’ve set “Allow Anonymous Inbound SIP Calls” to “No” and thought that I would find “allowguest=no” somewhere.

Does Allow Anonymous not toggle the allowguest variable? What am I missing? (I’m a noob so I’m missing a lot…)
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it is not used. The dialplan processes all anonymous calls and the setting determines if the calls are played an ss-noservice message or otherwise if they are processed.