POSSIBLE CAUSE
I have a guess why this is happening.
When the AI sees a bad guy, they retain perfect positional knowledge of it for a bit, even if they lose line of sight. This is their memory. However, they are able to engage targets they remember with extreme accuracy even after losing line of sight due to a stance change.
I assume this has something to do with the timing of whatever internal loop updates the knowledge of the AI relative to the enemies around him based on his 'sensitivity' parameter. The AI's memory should be weakened when they lose line of sight and change stance. No human could exhibit the behavior shown.