This "ultimate" test didn't work for me. My leak (on a Model X) was the rubber strip along the top of the drivers Door Panel on the INSIDE.
That rubber strip was supposed to contact the glass and it wasn't when the door was shut and the window was up. I had to adjust the glass to fix. So the "hot air" had to fill the whole door before escaping so nothing showed up on IR. But it sounded like the window was open.
Model 3 has a felt strip along that same spot against the glass so it's harder to know how tight/critical that should be.
Your idea is good, but I wouldn't call the IR camera the "Ultimate" test. Taping outside failed to locate my issue as well.
I found mine by putting a small towel along the top of the door panel and the noise was instantly gone.
As far as taping up method, he could tape the seams between the roof glass as well, which varies a lot with Model 3's (that also wouldn't show up on IR camera, nor the plastic triangle sticking out).
It could be an "Air Leak" or an "Air Disturbance" making wind noise. And a Leak might not be a direct path (like in my case).