It's interesting and something I've given a fair bit of thought to. So, you have your standard frogging SRT rig and you add a foot ascender, this allows you to step, but the problem is that you are leaning back too much to use your hand ascender. So, you add a knee ascender and get rid of the hand ascender, this is better, but you still have to "walk" with your hands, so it's like rope crawling.
Back in the day, people used chest rollers which were attached to a "bra" and then you use a foot and knee ascender to ropewalk.
This is how I understand it.
Sadly, the book assumes you are not lazy and have access to sailmaking equipment, webbing and a machine shop.
I'd like a bra with a roller. Thinking about it, they are definately the way to go.
With the standard chest croll and knee/foot ascenders, you waste a lot of energy walking up the rope with your hands....in theory, you should be able to relax and let the pulley do it's job.