I believe that you may have your terminology off or else I may have confused you.
If you are referring to "Pre Engagement Sequencing" I teach to top off the pistol. Many of those I work with are armed with .45 cal pistols, and a seven round magazine with one in the chamber leaves you with 6 rounds. That one round represents 14.285% of your total in the gun and that is your back up weapon.
One round down from 28 is 3.5%.
Ammunition is a funny thing. If you never press the trigger, you have too much. If you do press the trigger, you'll never have nearly enough.
In the case of the carbine, I am satisfied in not topping off (though have at it if you so desire) but want to ensure that the chambered round verification is accomplished and the magazine is locked into the receiver (PUSH/ PULL).
We do teach Tactical Reloads with the carbine. A loaded gun is a happy gun, and I can vouch for it as a TTP. Performing a Tac Reload when you can keeps the gun happy and good guys alive.
Hope this clears things up for you...