I've done that a few dozen times up in a tree. Maybe more. MS200T and MS020.
And at least one of those times I had forgot to flip the kill switch.
I would never suggest it though, the climber would have to come up with it on their own. It's really pretty easy after the motor starts to give the starter cord a quick tug and catch the saw by the rear handle. I would have to say that every time I did it I was out and on top of a limb and wanted to use one hand to balance along with my climbing rope. I would have had my lanyard around the limb I was standing on but it would not have been in a spot to use it well as a positioning point.
I've made thousands of cuts using one hand and many of them were one hand on the saw, the other hand catching or tossing the limb or pushing the bigger wood. Made a lot of use of the 'snap cut'.