It has been said that the LLVM bitcode is too low-level and architecture-specific to allow switching between x86 and arm for the final compilation pass that App

It has been said that the LLVM bitcode is too low-level and architecture-specific to allow switching between x86 and arm for the final compilation pass that Apple performs in the app store. It's more likely this feature is here to enable hotfixing compiler bugs and micro-optimizations and perhaps taking advantage of new features in new chips within a given architecture.