On my first climbing job the boss harped two hands on the saw, two hands on the saw. It just didn't make sense but these guys know so I was getting good at cutting and directing branches with my feet. This guy would would be awesome at that.
Later I got to watch their old vet and the boss work and they one handed steady. Talk's cheap as it turns out and rules made to be broken when it's safer not to follow them. I've also seen videos of guys one handing when they don't have to, just a bad habit.
It was a good way to learn though. A good handsaw can be quicker in under 2" conifer branches for example or rig more. No matter how fast, it's never fast enough, but it's easy to be safe enough.