You can’t test any air flow not using a standard test pressure. His Mickey Mouse test rig can’t flow enough air to even give repeatable test results, let alone move enough air.
If he used an actual flow bench for the testing and picked a test pressure of at a minimum of 10 inches the results would be different. Then he could have tested at higher test pressures and recorded the results.
Poor testing capabilities gives inaccurate results. You can bet the engineers who design and test these filters move way more air through them at much higher test pressures than he did.