I use it, it's more expensive than your 'traditional' white pumice, it looks much nicer than the white pumice IMO and it has performed well with a few of my trees (portulacaria afras, bucida spinosas, ficus benjamina)
In a repotting guide that I recently read from ABAS website (Peter Tea and Kathy Shaner's techniques compiled by Renee Shelly), it is recommended for drainage layer (page 12).
Credit to ABAS Bonsai, Peter and Kathy, and Renee for putting the guide together, it's a great reference point as a 'repotting FAQ'
they arent using it as a 'more coarse' drainage layer, it's just being used as 'equal particle size' drainage layer, all particles in the container the same but the lower portion with hyuga only. I'm just quoting what Peter Tea mentions, IMO it doesn't sound wrong.
The concept of 'super coarse' drainage layer is definitely long debunked, ie 3/8" drainage layer and 1/8 inch for the rest of the container.
Take it for what you will, hyuga is a more aesthetically appealing (IMO) form of pumice that performs well and is mentioned as drainage layer amendment in the guide that I quoted.
on page 8
"When creating your soil mix, keep the sizes of the individual components
as consistent as possible. Large particles have a tendency to work their
way up towards the top and small soil tends to work it’s way down."
same. im using 3/8" white 'ugly' pumice for development, but im using about 70%/30% hyuga/akadama for nicer trees whenever possible, it blends much better.
kiryu/hyuga also seems like it would be a visually appealing mix as well
only recently, I realized mach5 is sergio cuan (DOH!) and I have seen him dozens and dozens of times doing amazing demonstrations on youtube, I was wondering..."I know this guy from somewhere...his face is familiar"
This forum is truly a gem to have pros sharing their stuff.