Comment by onion2k

They're using git as a cache. Having generated files stored there means they're available if they're needed (eg in CI) without needing further access controls, they're versioned, and it's a simple and understandable strategy. As the article states, most devs are set up to ignore those files so they're not much of a source of the slowness. It's a common pattern for apps that have to serve lots of different locales.