Correct, I agree you run it with an eye on it (which you should probably do anyway) instead of firing and forgetting (which, to nginx's credit, is typically stable enough you can do that just fine).

That said, nginx treats experimental as something you explicitly run in production- when they announced they added it into experimental they actually specifically say to run it in prod in an A/B setup.

https://www.nginx.com/blog/our-roadmap-quic-http-3-support-nginx/