Well, technically, the "rule" means not to pay it down faster than contractually required to do so. :)
And yes, by that advice, if the current treasury note is 2.333%, you would not accelerate debt payments for debts below 7.333%. Of course, if the note rate went up or down, so would the
I'm not convinced that's the best way to do it, but I think you've understood the author's intent.