If an incredibly thin piece of plastic wrap can throw off the performance of a capacitorThat’s a wank too, as it’s not ac music signal they're showing the effect on, but minuscule mF capacitance the test gear leads (which they conveniently don’t show) are in different positions, and could even be cross over for some shots, this is more the reason.
Take any capacitance meter and it will show those minuscule mF or uF differences when measuring the same cap twice with the leads moved around.