If the weapon were loaded BP I'd suggest he was wrong putting his hand in front of the cylinder. With the R&D this is not an issue.
I'll submit that it's a bad idea to put your hand around it even with the R&D. There's no safety. If that hammer falls, you will get burned by the gases at the barrel cylinder gap. Definitely an issue...
You are right in that the cap and ball are more accurate once you work up the right load for your gun. I can hold a tight group at 20 - 25 yards (3" circle with the occasional flyer), but not with store bought cowboy action smokeless loads. I get better results with my own black powder cartridges, but still not as good as the cap and ball.
I timed myself last night swapping cylinders. I can do the "Pale Rider" in 7 seconds. The guy in the video just isn't that experienced yet. He could use some pointers before he makes a video.