Is that not a tremendous optimization for the team? It probably cuts the team size in half (or, seen another way, doubles its size for free), and it unifies of a lot of the mobile and web stacks behind similar languages and tools, which in turn would allow some unification in the hiring and recruiting pipelines.

This overstates the gains by a lot.

1) Each platform still requires a good amount of special attention.

2) The React Native project introduces breaking changes far more frequently than the underlying platforms

3) Being an abstraction layer, eventually something will break, and you’ll still need someone who understands cryptic linker errors and platform specific quirks.

There are cases where it definitely makes sense, but the hidden costs need to be accounted for.

I would argue to the contrary that it’s such a large optimization that even accounting for all of that it’s still a big net win from a staffing perspective. It’s far easier to maintain a few Android experts on staff than an entire department of them.

I understand that argument, and it's seductive, and in many cases probably true. But it's advertised as a 2-3x productivity gain and that is simply not the case.

It's an optimization they aren't using, React Native is only being used for Android.

Do they not clearly intend to use it for both in the future? They didn't go back and rewrite all existing apps, and they did an experiment with Android to validate the approach.