What is the Purpose of the "Always Use EKF" Flag?

Within the AP_AHRS_NavEKF::active_ekf_type function I can see that even with the Always Use EKF Flag set the function can still return NONE which switches the Active EKF Type to DCM. Within active_ekf_type if the always use ekf flag is set EKF2.getFilterFaults is called rather than EKF2.healthy. EKF2.getFilterFaults seems to be a less strict health check than EKF2.healthy.

So is the intention behind setting the Always Use EKF Flag just to make the Active EKF less likely to fall back to DCM? And in the event the Active EKF falls back to DCM would the Active EKF be more proactive in switching back to the EKF?

Are there any other implications to using the “Always Use EKF” Flag? And is it safe to use with ArduPlane?