I don't know. Piccolo says the KMHMH from Cell was weak because it's based off of the Saiyajin arc one, which could imply its amplification has increased alongside the years. But he then goes on to call it pathetic, which I don't think it's a proper way to adress an attack that is 2.2x+ above Cell's power and consequently way beyond his own... there are some other scenes that don't work too well with a 2.2x+ amplification either, as Freeza stopping Goku's Kaioken x20 KMHMH, albeit with difficulties, whereas the Kkx20 was already at least fairly close to the power he was using at the moment. I think AT was just not taking into account the multiplier displayed at the Raditz's battle anymore, and admittedly the implications of future amplifications and its relationship with user's power would work better were it not that high of an amp imo.