Ah, that is the official docs, but just an old version. You can see in the bottom left-corner that it says version v0.12.7; if you click on that, you can choose “stable” which means the latest released version of Convex.
Search engines giving old versions of docs is a common issue; we don’t really want to delete them because someone might be still using v0.12.7 and want to have the right docs for that version. But I filed Add banner to old versions of Convex.jl docs · Issue #460 · jump-dev/Convex.jl · GitHub to use some new Documenter features to add a warning banner in this case (maybe I or another open source contributor will get a chance to implement that, to avoid this issue).