TLDR: Native language wins over JVM optimisations.

In my recent but limited experience of working on iOS apps, they do need any performance boost they can get anywhere. Coming to the Apple ecosystem (appstore connect, testflight, xcode etc) it's quite a shock on how slow it all is (using xcode on a Mac Mini M4 for development, and as for web updates/approvals etc I now understand the pain others have mentioned here).