Yup, that is how old wive's tales work, repeated over many years. Repetition doesn't make it true. Certainly drive your car in a manner suiting yourself for comfort. Comfort is your rationale, not efficiency.
Where the test in the video was a part let down was that that the internal temperature inside the car was totally different. So he had the A/C turned on and got the temperature down to 23c where during the other two the temperature is at 28 and 27c. The second the third test was purely rather than having the car cooler, has a higher amount of air moving around inside the car. Now I would like to see if instead of setting the A/C to 20 and it running full time on the compressor and never actually getting down to that desired temp, if he would have done the same run with the A/C set to 26 (as that was the temp he said was comfortable with the fan set to 7 so you get the cooling effect of just air moving past your body. This way the A/C is only maintaining a comfortable temp and not running full time un-needed.
Also.. Please re-read what I posted. Your video linked I believe did show that there was a loss of efficiency between driving with the windows up and the fan blasting away, and driving with the windows rolled down 10cm. So YES you do loose aerodynamic efficiency. As well, I stated that in an ICE ONLY car the A/C is pulling the power off the engine. In the NIRO HEV it is electric so the A/C is more efficient compared to ... the ICE ONLY CAR. So how does what someone testing in a BEV have to do with anything? There is no ICE motor inside that vehicle at all. I bought my Niro Hybrid to replace a Gas Guzzling Crossover car. I didn't buy a Niro PHEV and clearly, I did not buy a Tesla or a Leaf or an E-Pace or any other type of BEV. I got a NIRO HEV.
The video went and tested the temp inside the car and it was a good 4-5deg difference. And he also stated that it was nice and quiet inside the car. Then you get to compare this with a car with windows wound down that is not only hotter (actual temp) but also much noisier. Yes with the setting chosen the A/C did use more power to run but how much more is it inside the Niro HEV?, and compare that to a similar size ICE only vehicle and what impact does that have on the fuel consumption?
I don't have the numbers, but if running the A/C in the Niro reduces my fuel efficiency by <5% I am not going to bat an eyelash at it, as I would rather have actual cool and none of the noise. (Heck, I have about 25-40% fuel efficiency loss running the heater and defogger in winter time for my comfort.) But all this is nothing compared to the on average 20% loss you get running an A/C inside an ICE car that is also multiple times more compounded with the fuel efficiency difference between my Niro Hybrid vs most every other comparable gas engines ICE car.
In your video test, you have a choice of getting 3.4% worse electric economy to get a cooler car with much less noise. I think I will take that any day at highway speeds. But everyones priorities will very depending on their wants.