The only thing for SURE, is that what you see can't possibly related in any way to GSX. The one and ONLY changes GSX does to FSX configuration are:
- It enables the Service door on the default 737 and 747, because the original aircraft.cfg from Microsoft only had 2 exits and no service doors, even if the model had all the animations
- It disables the default pushback vehicle, but that's just a visual model change, it won't affect anything else and, in fact, default Pushback will still work, just with an invisible truck.
Wing flexing is controlled by bones attached to the wings and controlled by a variable, either custom or default. FSX disable animations controlled by a variable after a certain distance to save fps, and/or the airplane might do it on purpose to animate only the highest (closest) LODs to save fps too. So it's just normal that zooming in triggers a different LOD and re-enable animations, so the animated parts will suddenly start to move.
Nothing related to GSX, of course. Its only "fault" is that, by its very nature, you will tend to look your airplane more closely than usual, so you might be mislead thinking that something you never noticed only appeared after installing GSX.