I agree with you. I don't think LLMs magically solve the problem that comes with writing twice.

Even if they were to write for two platforms, they'd likely want to have a whole bunch of business & state management logic that would be shared between the two with the native part being a thin platform layer.

It seems like a mostly shared codebase (reglardless of specific tech choice) would let them get precisely the end user UX they care about. Both for performance and capability.

Not saying they should use React Native but maintaining two large apps and using LLMs to keep them in sync seems far worse than many other options.