> For all the built-in types, I see the value now.

The same applies for non built-in types too though (e.g. http://docs.python.org/3.4/library/collections.html).  The only difference is that the built-in ones have entries in functions.rst and use more links.

> Is that not good enough?

Not really, and creating additional links and suppressing others with :noindex: feels wrong.  The idea is that :class:`str` should just work and link to the right place.