Listening Height Adjustment -- Is This Why Two People Don't Hear the Same?

Just wanted to pass on a recent experience, and surprise, in my system

My room (https://systems.audiogon.com/systems/5707) is set up for one person to listen. I have a medium height arm chair at the listening position and had always assumed that it left me with my ears broadly in line with the tweeters in my Magicos (i.e. 42-43" off the ground)

Well I checked and I was actually at 38-40" depending on how upright I sit. Wondering how much of a difference getting it just so would make I purchased a set of add on feet, each 3.5-4" tall and added them to my chair -- not a good look!

But wow, what an improvement in sound. Tonally the speakers take on a very different balance, upper mid range and vocal intelligibility is substantially improved, bass is lighter but better defined and overall integration across the frequency range is much much better than before

The odd thing is that I don’t have the tweeters pointed directly at me -- they’re angled about 2’ off to either side, so what would a couple of inches in the vertical make such a difference assuming the tweeter drop off is uniform in all directions? Is it more a matter of driver integration?

This experience leads me to wonder
a) how many of us have actually measured and adjusted our set height to optimal/tweeter level, and do we do this every time we audition a new speaker, and
b) if two individuals are not the same height do we adjust for the difference in height between them sitting -- say a 5’6 vs 6’ person that’s probably a 3" difference sitting -- unless your chair has adjustable feet the experience of the two individuals may be completely different