I've seen that video and I'm not sure if ever addressed the flaws in his testing
The CPU & GPU throttle limit themselves to work within certain temperatures and he never provided what clock speeds both items were outputting.
Also, if he's running the test with both fans at max speeds, that doesn't match everyday use cases, majority of users want their PC to be quieter, not louder, which he doesn't show either.
However, you could be the person to prove David right. I haven't seen anyone else really test this out as its always just been a rule of thumb to always have intake to create positive airflow within a case for best temperatures and reduction of dust.