You are of course correct that some React components will not be caught by this single-line test. It is impossible to truly know unless you are the author of the app, and that's the case even with React tools (e.g. you would not be able to identify my server-rendered components that are not mounted on the front-end).
The intent was not to provide a debugging tool - it's just to provide people with limited exposure to React a simple one-liner to help them understand what is meant when someone says Facebook/Instagram use React, and see some components in the wild. To that goal, using a simple test for data-reactid attribute will catch the overwhelming majority of in-the-wild use cases.
The intent was not to provide a debugging tool - it's just to provide people with limited exposure to React a simple one-liner to help them understand what is meant when someone says Facebook/Instagram use React, and see some components in the wild. To that goal, using a simple test for data-reactid attribute will catch the overwhelming majority of in-the-wild use cases.