Refining search results by clicking facets with multiple words does not result in a subset of the prior search, since all words in the facet will be considered individually for the construction of the search query.

Steps to reproduce

In a clean installed eZ Publish 4.5 (eZFlow with demo content + ezFind 2.5), search for the word "publish"
One of the keywords returned should be "enterprise search (2)"
If you click this keyword, instead of 2 results you will get 7 results. (because any article with either "enterprise" or "search" will be considered as valid)