Some of us have already talked about it in this forum
https://answers.unrealengine.com/questions/141532/releasing-for-android-size-workaround.html#answer-203991
look for my comment to my answer i think you are suffering from what we just did.
And to answer your question tappy chicken for some reason has a smaller engine library within its apk its content is 13.5 mb all uncompressed in the final apk.
All of us are using a engine library that’s 60mb → 20mb compressed
they are using 43mb → 13mb compressed
Why? How? Magic? noone from unreal has really answered any of us till this point.