Yep - the spark plug sales wars! All of these designs have been around for 50 years and more - and yet, mainstream plug design hasn't changed (other than longevity) in that time - that should tell you enough.
The video is typical amateur stuff - no attempt made to find another cause (or explanation) for the difference in consumption. It is an EFI engine making it very easy to check why it used less fuel (was it atmospheric pressure changes, air temperature (both will have changed over a short time) or something else? Also, these "mature" (i.e 1990's) EFI systems are pretty crude by today's standard - they used simple look up tables for fueling with no interpolation (they "switch" between different fuelling rates) on sometimes very minor changes in sensor readings.
And last, and most importantly of all, no repeatability (the 1st law of any research!).