Yeah, I think its actually one of the least explanatory videos the headphone show ever made. I wouldn’t show it to anyone who is new to the Hobby honestly. To make it short: graphs give you a pretty good idea about a headphones tonality. And if you know what you like and how the headphones you like measure you can often tell how another headphone sounds in comparison through the graphs. But since your ears work different than a measuring rig you will always need to listen to the headphone to actually know if it sounds good to you.

Frequency response, as a physical property of a headphone or IEM, dictates what you will hear (barring deliberately added DSP or exceptionally poorly designed edge cases). That doesn't mean that graphed measurements of said frequency response will necessarily tell it to you. The two are different things, which is the source of much confusion.

>oh wait, actually frequency response tells you literally everything you could possibly want to know.

For iems, frequency response tells you almost everything.