AND-ing of labels ins RSS feeds

As far as I understand the documentation and tests are showing the RSS Feed Builder combines labels with the logical OR operator.

I would like to AND the labels when building an RSS feed - either manually or by the RSS feed builder - instead of the present default OR-ing.

Regular Confluence label work (e.g. contentbylabel macro) allows explicit logical operators by adding and/or signs to force or exclude the presence of a label. When working with rss feeds this doesn't seem to work.
AND-ing means: "...matches all of the labels...". If I adapted the logic to the contentbylabel macro I would write 'labels=+hummingbird,+blackbird' (show me all content about hummingbirds and blackbirds - but not content labelled with only one of 'blackbird' or 'hummingbird').

An analogy to contentbylabel might look something like:
http://my.wiki.org/createrssfeed.action?types=blogpost&...&labelString=%2Bhummingbird,%2Bblackbird&rssType=atom&maxResults...os_authType=basic (URL-encoded + and even - signs)

And what would be even more comfortable is the explicit exclusion of labels: Show me all content that provides (at least) the labels "bear, dog" but not "cat". If I adapted the logic to the contentbylabel macro I would write 'labels=+bird,-hummingbird' (show me all content about birds, but exclude content about hummingbirds.").

As I noted I am looking for the label functionality (use of logical operators) in rss feeds (Feed Builder, generated URLs) I know from the contentbylabel macro e.g..