That is a great video, and explains sound quality in a way that is easily digestible for the uninitiated. I can't verify it's authenticity, so I am waiting for other reviewers to do the same type of comparisons.
I was one od those upset they removed the headphone jack because I have not had great experiences with Bluetooth either in my car or headphones. I am not an audiophile but can clearly hear The lightening to USB connection to my car stereo however works great so my main issue was the possible degradation while using regular headphones.
When I first heard they were removing the head phone jack, I got really upset because I have never had a good experience with bluetooth sound quality either in my car or with my phone. Honestly, I am not overly in love with the DAC on my iPhone, but I don't use headphones enough to warrant the investment. in an external one. Even though I was one of those railing against the removal of the port, I held out hope that Apple would deliver a higher quality listening experience to go along with their money grab for accessories. If this video is correct, I think people will realize that sound quality with the dongle, will be poorer than sound quality with headphones that use the lightning port. And they will improve sound quality for bluetooth using their bluetooth products "effectively" herding people in their proprietary direction. Like the video said, the loss in sound quality is not stark, but enough to acknowledge the difference.
They video really did a good job of explaining sound quality and how its transmitted through the phone, dongle, and headphones.