IPsec VTI routes not applied at boot time when gateway monitoring is disabled
With gateway monitoring enabled, an interface event kicks off a restart of other scripts which apply the routing and then the route is present in the table.
With gateway monitoring disabled, the route is not present in the table at all.
Looking at the code, the IPsec interface configure explicitly does not set routes at boot time, which is likely the cause. Removing the check lets it work and appears to have no negative side effects.