That's the only reason I'm guessing it's fake, because of the amount of current compared to the other charger. Otherwise the charger looks as good as the original--very minor cosmetic differences only between the two.
However, the genuine AC10u charger isn't a stellar performer either. I have a no-name charger that outperforms both in terms of output. So the genuine AC10u isn't current limited by the SoC of the battery.