You're comparing Go to RN. The comparison he's making is Matcha to RN. Matcha doesn't come from a giant company. The language it's in does, but that doesn't mean anything for framework momentum.
We are discussing about the framework itself and not go as a language.
The framework is a nice idea, and will definitely help into diversifying some of the mobile frontend stuff.
On the other hand you can't compare RN to this framework.
As the person you commented on, facebook has been using RN on its main products like instagram, so it has proven that the framework can be placed on production ready apps with a massive userbase.
That's not really a direct comparison. We're not talking about languages here - it's the framework. React Native is used and developed by Facebook, whereas Matcha is used and developed by no one notable (afaik).