erm, removing a cover plastic or otherwise would have no affect on the sync timing of the flash/shutter.
It may enable to camera lens to pic up images more clearly and even stop a glare effect from the flash but nothing more. Besides i dont have a cover on my iphone5 at all an still the issues remains.
The issue mentioned here is a clitch that causes the camera shutter to lag behind the firing of the flash.
When i got my iphone5 I restored my iphone4s backup from itunes and after reading other threads regarding various other issues it seems highly possible that restoring from an older handsets backup MAY be the cause of some of if not most of these issues.
I have now fully restored my iphone5 to factory settings an set it up as a new phone. Time will tell if the flash/shutter sync issue is gone or not.