My logic is that it looks more natural using a few small split shots, rather than a single large chunk of pencil lead. To me, it looks like a couple small rocks suspended in the current (which isn't really uncommon in fast water if you pay attention while wading).
I also find when "bobber dogging" that the split shots snag up a bit less than a pencil lead.
In the end, it probably really doesn't matter to the fish at all. It's just whatever you're most confident in. Back in my first year fishing the Vedder, an old timer (been so long I can't remember his name - Fred I believe) took the time to show me his set ups. He had hit 3 fish behind me in a row behind snipers the one day when the river was beside the road before the flood, and I asked him for some help. I started hitting fish right away using the split shot and never looked back. He felt it gave a more natural drift, and I agree with him.
PS. for the worms (as said in the video), don't be afraid to go heavier on the leader. Fish smash them hard, and I really don't think they care about a stealthy presentation when eating a big pink thing.