> Экспериментальные версии как и с самого начала существования проекта - в экспериментальной
> ветке.

nginx 1.25 - не экспериментальная ветка, а основная, т.е. рекомендованная к использованию, стабильная и с новыми фичами.

https://www.nginx.com/blog/nginx-1-6-1-7-released/

We recommend that in general you deploy the NGINX mainline branch at all times. The main reason to use the stable branch is that you are concerned about possible impacts of new features, such as incompatibility with third‑party modules or the inadvertent introduction of bugs in new features.

http://mailman.nginx.org/pipermail/nginx/2014-February/04208...

Just a note for people who worry about using mainline version in production.
The fact that there is version called "stable" doesn't imply that the other one
is "unstable".  We call one branch stable because we maintain internal API and
feature set stability for 3rd-party developers, while mainline versions gets
all improvements (and even more bugfixes).