Restricting results by clicking letter (A-Z) after an OR search doesn't restrict but rather WIDENS results

After doing an advanced search with the OR operator, I want to restrict the results of my search further by clicking on a letter above the search results (R, for example).

What this SHOULD do is take my search results and narrow them based on the letter I click on.

Instead, this uses the OR operator to combine my current search with a search of every contact starting with "R", actually increasing the number of results most of the time.

Here's the documentation where it says the results should be narrowed: http://wiki.civicrm.org/confluence/display/CRMDOC40/Sorting+Results

I reproduced this in the current demo site. (Screenshot of search summary attached)