I think all you want is a single event that says "Every tick, position child to Master imagepoint "SpawnPt" and set angle to Master.angle".
If we make mirroring affect the pin, then shouldn't flipping also affect the pin? If not why not, and if so how would that work? The pin behavior doesn't know you're trying to attach it to an image point, it just preserves the relative distance and angle. It's such a simple behavior and trivial to reproduce in events (in this case one event does it), so I think it's fair to say if the behavior doesn't do what you need, rebuild it with events.