Don't think this one holds water. Never Have, Never will.
I have spent much much more time on the water than my Brother-in-Law.
Just the phrase "time on the water" doesn't mean that what you learn or do during that time is correct, or helps you become a better fisherman.
If you add the "additional" statements that SFAJacks44 stated along with "time on the water" then yes it is applicable.
I think you have to process the data you get, while on the water, to better develop your skills.
Fishing is a "skill", much like any other sport or activity. Just because you go play golf 3 times a week doesn't mean you will become a scratch golfer.
Just because I fish 3 times a week for 6 hours a day doesn't mean I can go fish on a professional circuit