In my opinion using a saw is all Hollywood smoke and mirrors if you have watched the youtube video it was not a real-life event
he would have staged it for video knocked post in not to hard so it would come out easy it would be embarrassing if he could not do it on youtube
He only cuts top 1/3 of tube and he cheated because youtube is supposed to show people how to do things and nobody would have a pneumatic hammer power tool

The drill was so easy if I did not have one, I would have rented one, if they did not have a steel drill a masonry one would do for aluminum.

You could also drill out a steel seat post but would have to use sort of cutting fluid on drill or even light oil would do.

Got post clear to 9-inch depth I always have my saddle 5 inches above so I am leaving it as that.