Despite following Unity best practices, my iOS game bloat from 20MB to 60MB. Why?

Our game, Drive Across, recently launched on the Apple AppStore :

It is a single level game with an intro.

We followed all best practices to minimize file sizes (Unity - Manual: Optimizing the size of the built iOS Player) and (Unity - Manual: Reducing the file size of your build).

When built using Mono scripting, the IPA was 20MB. Owing to new Apple submission rules, a Universal binary was required and we used IL2CPP scripting to generate a 35MB Universal binary.

Despite all best efforts, it is quite surprising & disappointing to find the app size on the store become almost double, to 60MB.

I am inclined to believe IL2CPP builds generate binaries that do not get optimized as easily by Apple after they DRM-protect files, and it would be very helpful to the developer community if Unity can add further information on file size optimization.

Have you tried not recompressing pngs in xcode?
That tip is surprisingly little talked about and helped us reduce the IPA size 13 megs from 70+Mb and appstore size almost double that.

Supposedly that setting could decrease performance or something but we didn’t see any difference whatsoever.