This is (effectively) false. You don't need to eject to use third party modules (including, but not limited to, react-native-webrtc). You can use expo-dev-client to build your own "Expo Go"-esque development app, and EAS Build provides a fully transparent build environment.
To be precise, EAS Build does actually eject IIRC, but you never notice this during development. I haven't ejected or seen an android/ or ios/ directory in the past year of developing an Expo app, using many third party libs.
You then use 3rd party modules (or build your own) to add/extend native functionality that is exposed to react native. For example, webtrc: https://github.com/react-native-webrtc/react-native-webrtc