Ok, it is funny that you have fallen for this.
Think of it.
He has a small carb (Looks to be for a 2 cyl like a 22 or 24 hp engine, not a 5hp B&S)
He has an electronic contraption, that he barely discusses, but it has: 1, an O2 sensor. 2, a way to control air fuel ratio(air leak ??), 3 output to a smart phone app. 4 a vacuum sensor. And I bet others.
Sounds like a fuel injection setup. I'll bet he has an injector in the base of the intake, making a TBI setup, using the carb as the air valve.
Back to physics. If he is keeping the air fuel ratio within normal limits, he cannot be doing any better, or worse then any carb. Same RPMs as before, Same engine, same air fuel ratio, therefore, mileage cannot be much better, or worse then before.
Without changing the RPM's, or engine volume, the only other way to get better mileage, is to use less fuel per revolution, IE go lean.
What he does not show, is the car accelerating. You can get great mileage with any carb, by driving like there is a egg on the gas pedal (I bet you have heard that before). I'll even bet most of that course he drove, was down hill.
Keep posting his links, he needs the money. 🤮