Those #'s are "SLIGHTLY" high - IMO. I won't quote any numbers, but most electric fans actually run slower at idle and how much slower will depend on just how much your alternator is up to the task at idle, where it supplies much less current. A flex fan actually works just the opposite from your explanation. There is much less HP loss at speed ( higher rpm's ) where the blades flatten out -( reads "FLEX" fan).
Yes, if you have a properly designed electrical system, it won't slow down. That only happens when your alt can't keep up with the demand and maintain 14 volts.
And once again, a flex fan takes less but not "much less". The flex fan, especially without a clutch, consumes a lot more hp at high rpm than you think. Look at the tables.
Stick with your Doctor's hat.
You can stuff that attitude. I may not be as much of an old-timer as you (built my first big-block A-body around '83) but I know what works and what doesn't.
