I really have nothing else to add except that bitcode wasn't enabled, the same game was ~60Mb when we were testing it with TestFlight, after uploading it to the store the game just became 422Mb, why is that ?
Enable bitcode. That allows Apple to recompile the app for each chipset, and then they only ship the relevant one to each customer. With bitcode off, all of the different code bundles end up in your app, making it bigger.
Honestly, I'm surprised they let you submit with bitcode off.
turns out the size we see in the appstore is not the "Download size", instead it's the full size of the game after being downloaded and installed (which mean decompressed), comparing that to the TestFlight version size (on phone storage) they are pretty similar.