For those of you unaware, Apple is required to approve every app update (and every new app) before they are allowed to go live in the Apple App Store. Apps on the Android Market/Google Play Store is a little different, app updates go through automated checks to make sure they are not filled with malware and go live within a few minutes. That means that while MCPE for Apple devices is going through the long process of approval, they can continue to iron out bugs on the Android/Kindle versions. See the source link for the original tweet.
Source: Twitter