Yes, but I think the OP is talking about the new variations in how much AAnyTIme costs from one travel date to another, and is talking about changing AAnyTime to AAnytime (that's not upfaring, is it?) and keeping origin/destination the same and only changing travel dates, but yet because of travel date changes the number of miles required changes.

This is a new situation, but it seems to have an old analog: What if you booked a US->Europe coach award at peak SAAver levels, and wanted to change to a non-peak SAAver date, and there was SAAver availability, and your origin/destination was not changing, and it was more than 21 days before departure? Would they credit you the difference in miles but not charge you any fee? And vice versa (peak to non-peak date change), would they just charge you the difference in miles but not charge you any fee?

(And that site you linked doesn't seem to explain either situation at all.)