I get what you're saying,
But in the Bulletin book, it is no where stated that these numbers were related to RWHP. And since the charts have been around since the 60s, I assumed they were flywheel. And since the numbers have, for me, always correlated to flywheel hp, that's what I assumed they had to be. Further,if those charts are RWHP, there would be no way to predict your mph using those charts,and using your engine dyno results, (unless you fudged the powertrain loss, with a pick-it-from-a-hat factor), so they would be kindof useless, for anyone wishing to hit a specific mark.
If you're right, then I've been wrong for a lotta years.
On the bright side my engine just gained about 75 hp.