I stumbled onto some videos recently by a guy named Chris Korich. I've heard his name for years, but I heard very little other than his name. He learned fly casting in California with the Rajeff brothers and is a highly respected casting instructor. Anyway ... in his videos, he mentioned that he liked to teach people using older graphite rods and fiberglass rods because they have a softer action, and the student could feel the cast better.
Here are his videos, if anybody's interested:
https://vimeo.com/user4826342