I've taken some of his general ideas pertaining to "Intensity is King" and have implemented it into my training approach. However, the program as a whole, I haven't experimented with.
If you don't have easy access to weights, or a pulley, I think it's a great program. It appears to be set up in such a way to be "self-limiting" so you don't get injured. There's an argument here over whether or not you are stronger on subsequent workouts since much of the feedback is perceived as opposed to numerical.
When I am traveling, I take 2 Tension Blocks with me and will switch to this program for the days of travel depending on which phase I'm in.
In terms of tendon strength, it appears to be exceptional. In terms of muscle strength, I think it progresses much slower. Good/bad, that's up to you.
For me, personally, I've seen incredible gains using the repeater protocol. Until I begin to stagnate with that protocol over several seasons, I likely won't switch to anything else. If I was traveling all the time, this program would likely be my primary approach.
"My endurance is low" is a common misperception. I've seen a couple of your posts over on Mountain Project and I think your focus on endurance is misdirected.
Increasing strength will increase endurance. Increasing endurance will not increase strength.
To answer your question directly, density hangs have to do with tendon and ligament breakdown, thereby causing tendon density to increase over time. They are low weight, long duration hangs (to muscular failure!) to cycle through all the fibers in the tendons. You may very well gain strength in the process, but my understanding is that that is not the focus of the density hang.
I'm just trying to get some endurance on the hangboard because I don't have access to a wall right now.
I would embrace this as an opportunity to get really freakin' strong without distraction. Then when you have access to a wall again, you can focus on power and skill acquisition. Skill will play a huge part in your endurance journey.