Teaching People to swim without being in the water! Logic?

Dale's Cone of Experience tells us that if you learn something by hearing it, you retain 20%.

If you are doing something, you retain 90%.

Today as I was swimming in the pool, I happened to see a guy sitting by the poolside teaching a student who is in the pool how to swim, how amazing is that!

As I was swimming while seeing such a scene, another issue popped up in my mind about how a 35 years old Dr. is telling a 55 years old patient how to live in a healthy way up to old age, say 75 years old. How amazing is that.

Think about it, why not ask a 75 years old folk how they live to that age?
Wouldn't that be a little more logic?