You're right! Thank you. However, there's still a problem. A user searches for a technical term, and the carefully written glossary entry defining it does not appear.

For my search term (iterable), there was a single entry with a link to the Glossary page, whose associated text was simply the first few entries in the glossary.
===
Glossary
...active shell when entering code for an indented code block or within a pair of matching left and right delimiters (parentheses, square brackets or curly braces). 2to3 A tool that tries to convert Python 2.x code to Pyt...
===

On a related matter. Sphinx provides an anchor, used for internal navigation with the glossary. But it doesn't provide a permalink to that anchor. Compare 
https://docs.python.org/3.5/glossary.html#term-iterable
https://docs.python.org/3.5/reference/compound_stmts.html#with

I think there's a real problem, and that my initial diagnosis was wrong. So I've changed the issue title slightly. (I hope you don't mind.)

The problem is, perhaps, that it is the glossary page that is indexed, rather than the glossary items. Another fix would be, as you suggest, pop up at top of results page a glossary item.