I don’t think so. If you change to stable, you’ll only update to major releases, and 3.0.0 hasn’t been released yet. The last stable release was 2.8.0 (you can see latest updates in release-notes)
I don’t think Stephen was trying to be funny. Stable is used in a meaning of a keyword for app.yml, not as an English word. Reason being, the other (default) keyword, tests-passed can be described as stable too: it’s unlikely to be broken[1], and in fact, can be more “stable” (English-wise) if you update plugins and/or theme-components more frequently than you wish to update Discourse.
in my 2 years running Discourse, I’ve never had a situation when something was broken because of some fresh commit ↩︎