React Native under the hood uses Obj-C to bridge to native Cocoa frameworks. For example when you uses a <View> tag in JavaScript, it ends up calling iOS UIView.

Still, it's not the very same tech. Especially in this discussion, where we are talking about apps performance and languages, which need to get under the hood instead of talking directly with the engine, are presented as "worse".

Only a tiny fraction of the Facebook app is actually RN. Messenger uses none of it for performance reasons.

Huh? Isn't Facebook advertising their main app as no.1 use case of ReactNative?

Advertising is one thing, reality is different. The main, performant views are native. Some of the esoteric stuff is RN.