I am getting it now.
To get to see the individual shaders first and then analyze the Principled BSDFs as a whole like this was just a great idea. Still taking a lot of notes on everything, there is a lot of info here. I am going to rewatch this more than a couple of times to try to understand the Principled Hair, that was a nice surprise.
P.S
I have not been this excited over bubbles since I was a kid.