Clicking Connect VPN on the IPsec Status page establish the tunnel
In 21.02, interesting traffic has to be generated to bring up an IPsec tunnel. Regardless of whether pfSense itself can generate interesting traffic, navigating to Status>IPsec and clicking Connect VPN will not bring up the tunnel. If I generate interesting traffic from a host, the tunnel will establish.
Repeating the same test between two 2.4.5p1 firewalls, I can click Connect VPN before generating any interesting traffic (and with Automatically Ping Host disabled) and the tunnel will establish.