Thanks Suzanne, I hadn't seen that video before. I have done tons of sculling drills and they are like play time in the pool during a practice session. As to the articles by Hines that Donal F referred too he also talks of them as drills as Suzanne mentioned. They are meant to help with the feel of the water pressure as the angle of pitch of the hand changes. Hines also states in one part (2 or 3) that the most optimum pitch for freestyle is the vertical pitch and straight back. The other strokes, butterfly, breaststroke and backstroke rely more on changing pitch angles during the stroke.
I especially find the sculling feet first on my back as my favorite with hands at the side, great core workout keeping your rear up at the surface. The one I have the hardest time with is the feet first on your stomach hands out in front of your head. You (well at least I do) have to keep a lite flutter kick going to keep your feet at the surface and stay balanced.