rc.local is executed at login by rc.initial, and not at boot time.
See https://redmine.pfsense.org/issues/10978 for context.
/etc/skel/.profile is copied to .profile in all users home directories when they are created, including admin/root. This file contains a (incorrect? The test fails when you log in via SSH) test for interactive mode that executes /etc/rc.initial if the test returns false. In effect the goal seems to be to execute /etc/rc.initial whenever any user logs in non-interactively.
If this were working as intended the /etc/rc.initial script for every user who logs in, every time they log in, if that login was non-interactive. This seems like a mistake on it's face. However the script is not working as intended, and it is executed every time a user logs in, even interactively. This is easy to demonstrate by creating a simple /etc/rc.local script that echoes something to the console. The echoed message will be displayed every time you log in interactively.
The bigger issue is that /etc/rc.local should only be executed once, at boot. It should not be executed every time a user logs in, and it should not rely on a user to log in in order to be executed. This is a long-standing BSD init script that exists to facilitate simple startup routines that don't merit an entire rc.d style startup script in e.g. /usr/local/etc/rc.d/. I don't believe that pfSense ever uses /etc/rc.local for anything itself, and this bugs makes it difficult to use for admins as well.