I think your entire premise of the "test" is flawed, not mention methodology. Gas pressure changes with temperature, more so if the gas contains water vapour. And the Nitrogen gas in tires? It's about using dry gas (without any moisture) to fill the tire, so there is pressure stability for changing temperatures in critical applications. Like MotoGP, F1, or .... aircraft tires.

If it is about seepage, why not CO₂ which is an even larger molecule than N₂?

But I get it. If I had a YT channel I would also have some controversial topics, or make slight mistakes, or have an out there opinion sometimes. It's all about the viewer engagement for channel monetization