How does Nextjs justify using React canary branches?

I’m not a Nextjs user but was looking into whether I want to use it. I noticed that Nextjs 14.0.3 includes a canary build of React.

https://github.com/vercel/next.js/releases/tag/v14.0.3

How in the world is this acceptable? Does the React team maintain an extra branch labeled “canary” just for fun even though it’s actually stable?

Were people who are using this React framework in production right now using React canary before Nextjs?

Assuming the concept of a canary branch still has any meaning, how would a React framework that uses canary React actually be stable?