It's the best solution if you want a low profile adjustable gas block that will not move without your intervention. The way it works is pretty ingenious. I wouldn't worry about it if you plan on getting one. The detent is pretty strong and takes a good amount of force to press so it will not move on its own.
Yes when you screw it all the way in it shuts off the gas and turns the rifle into a single shot. I have tested it and it works.
The set screw is pretty long so you have a good range of adjustability before it comes out. I wouldn't hesitate to buy another one for my other suppressed rifles.

