I do not know much about React, but my impression is that this is not a framework per definition. My knowledge of React is that it is more of a collection of Javascript libraries that you can pick when you need. As long as you use Javascript as client "engine". So it is higher level of freedom compared to frameworks. You can pick what you need and do not carry a heavy backpack that slows down your site (like many frameworks).

AFAIK, React relay much on "shadow DOM" that makes it potentially faster.

Please correct me if I'm wrong...