He is talking more about using sharkbite to do a complete plumbing job. I'd never recommend that. And I sure as heck would never use one in an inaccessible location.

To plumb a whole house, use soldered copper or crimped PEX.

Only place I ever use them is to (a) transition from one type of pipe to another (which he admits is a great use for them), or (b) as the final connection from the home's plumbing to the fixture in an exposed location (so under the sink, behind the toilet, etc). Never inside a wall or another concealed location. Also worth noting there are some locations where using a blowtorch just isn't practical when you're doing repairs on a completed home.

You do have to be careful with sharkbites. They seal with an o-ring. If you nick that o-ring during installation, it will leak at some point, even if not immediately. When I'm replacing one valve, I can be careful to not nick the o-ring. But if you're plumbing a whole house, that is an awful lot of unnecessary failure points to use them across the board, and a contractor isn't going to be super careful with every single one.

Also worth noting that a professional plumber can probably solder a joint every bit as fast as Joe Homeowner can install a sharkbite. So there is no real savings there for the pro. Personally, it takes me a couple minutes to get a solder joint I know is good...probably closer to ten minutes if there was ever water in the pipe as I have trouble getting pipe fully dry for some reason.

Basically, for after-the-fact repairs and upgrades, they are great. For new construction, they are a horrible idea. As long as you are careful, they work well, though.