Tweettapering the t3 gives your thyroid a chance to start getting back to normal before you are completly off of the hormone. If you could take a hormone that would jumpstart you t3 levels after your cycle, like clomid does for your testes, it would be easier to stop cold.
Before people knew the benefits of clomid, hgc, etc tapering was common practice.
I agree that you could stop t3 cold and eventualy your thyroid would kick in, but I believe that just like with test, you would lose your gains...or in this case gain back your weight because of a slower metabolism. JMO