It is. The standard library documentation is part of the manual which is linked from there.
Regarding the URL that’s the old OCaml website. Regarding the caml name you might want to read a bit of history.
There are projects on the way to provide this on docs.ocaml.org. Note that if you are only interested in the documentation of the libraries you install in your opam switch, I suggest using odig this will provide you the docsets for your opam install base for your offline reading pleasure (to see a sample output of the tool head to http://docs.mirage.io/)
Aside, it is a wonderful source of amusement to me to see people (rightly) bitch when there’s no documentation and still (unrightly) bitch when it exists because they can’t be bothered to actually make the effort to look it up. The number of instances where I get questions about my libraries while the answers are a click away in the API docs is astonishingly high.