If you put the hotspot at different location on each image frames
And if you set the initial frame to another than the first one (0)
It won't take the hotspot of that specific frame but the same as the first one.
Even at runtime.
I made a capx in which I set a sprite with 2 animation frame and 2 different hotspot position (middle and bottom)
As you can see the only way to have the proper hotspot position is to change and go back to the animation frame (see the event sheet)
So I guess it's qualified to be a bug (: