A high scope mount will exaggerate scope cant.
The experiment shown in the video did not test the effect. Their scope was aligned to the bore, and all they were doing was rotating the rifle slightly on its axis. If their scope mounts had been twice as high there would still have been no difference. However, had the scope been mounted with a 5 degree cant, yet aligned vertically and horizontally with the target (as it would be, naturally, as your eye compensates for the cant) then there would have been an increasing effect as the mounts got higher.
The below quote from
@Muir suggests to me that cant is quite likely to be induced through poor scope mounting, as I have described above, and the experiment has no relevance to that situation.