In the video, the guy removed more wax than he put onto the board, thanks to the wax remover base cleaner.
Remember, brushing clears the wax out of the valleys of the structure. So, if you're just rubbing on wax then brushing it, you're just clearing the wax out of the valleys and polishing the wax on the peaks of the structure.
The rotobrush is still a brush, with bristles, like a brush mounted on a mandrel, so you still get the brushing action, like a hand brush, with much less effort, the power drill is doing the work for you.
When you just "surface treat" the wax onto the base, it doesn't really last that long, and shorter on more abrasive conditions, so you'll need to wax it more often.
Rotocorking, creates more heat than a nylon brush, which is why in racing, back when high fluoro overlays (if using the block form of the overlay) where used, you cork first, then brush out the structure of excess overlay, then after a run or 2, back in the waxing wax for another layer of high fluoro overlay.... where fractions of a second count in racing, and they are not known for durability, since it doesn't penetrate deep into the nooks and crannies of the base polyethylene. The durability of the wax is from the hot wax job under the overlay.