So this is video of Merc vs Red Bull's wing deflection during the last race with a grid:
Some of the video commenters point out something really interesting though - the Mercedes' "shark fin" is flapping around like a flag. Which is interesting for a couple of reasons:
The fin is an aero element, and aero elements are not allowed to move, so aren't Mercedes technically in violation of the same rule they've filed a complain against Red Bull for?
If the fin flapping around (against the rules) provides no advantage, why allow it? Flexing parts lead to failure due to materials fatigue which then causes accidents when the vehicle's handing characteristics suddenly change.
If the fin is generating a low pressure zone over the rear wing by spinning up vortices, it could stall the wing leading to lower drag at high speeds, which would be conceptually identical to a bendy wing that reduces drag at high speed