The amylopectin details may be right, but the rest is wrong. Conbini's sell brown rice onigiri (look for 玄米), it's just usually a very limited selection. They don't fall apart, and you eat them the same as normal onigiri.
After posting this comment I then decided to look into it (in my usual way) and just looking for homemade brown rice onigiri what I found was that at least the couple of recipes I looked at used short grain brown rice (which I did not even realize existed) and/or recommended using more water than usual.
Whole Foods carries a store brand short grain brown rice at a reasonable price that I really like. It’s one of my go-to rices and essentially the only thing I go to Whole Foods for, as I haven’t found a comparable product or price point elsewhere. I think it’s about $2.50/lb these days.
I just finished some tonight, and I’m certain it’s sticky enough to hold its shape.
Yup, if you want to do it at home, make it a little bit mushier. I don't like it, but it is very doable. Commercially they may use a binder, I don't know, I just wanted to make sure people knew they're available!
I did it tonight and when i picked up the rice i used wet fingers to give it just a touch more binding ability. Worked well. Kids loved it. Am excited to eat the brown rice onigiri tomorrow.
There is no white rice plant. It's all brown rice with the bran removed. Brown short grain rice doesn't have different starches than the same rice without its bran.
It would fall apart and be very difficult to eat.