Nope this is intended behavior
If an admin wants approval it is just that approval hense if a user makes a change to any image it is marked for approval again so that you can approve the change they made just like with a normal upload.
We listed to the majority of what our users want when coding features. If admin want approval they get just that. If you would like to ask how to modify your install so that on edit the image is not set back to approval then you can discuss code modifications at http://www.photopostdev.com