Honesta Missio holds the first enemy under her crosshair: an enemy behind it no longer takes the lock, and another enemy takes it only after 0.3 s in her sights, so the build-up no longer resets while she aims.
Big enemies can be held and marked wherever she aims on them: a Factory Strider's hull, a War Strider's legs and armour.
War Striders are her foes from the moment they spawn, so Persecution marks them and Memento Mori hits them without casting Honesta Missio first.