That’s right.
If you want to narrow your search to keywords AND tag go to the “Advanced”-button in lower left of the search window and filter for “tag” “is” and then type your keywords in the search field. Or filter for both in the criteria and the search displays the result just like a smart group would. (If you hit + to the right of the search field you could directly save this search as a smart group.)
There was a good discussion about this here: [url]Tags should be equal citizens when searching!]
Kind regards,
Bernd