Am testing search by tag. Simple search - one tag (in the test #TwPhCh001).

I'm trying to understand the different results I get.

Search for that tag via the web logged in I get 40 hits.
Search for that tag via the web anonymous I get 39 hits.
Search for that tag via the API (signed and authenticated) I get 36 hits.
Search for that tag via the API (signed with no auth) I get 35 hits.

From what I can see - the difference 39-40 and 35-36 is the same image. This
seems to be tagged #TwPhCh 001 (with space). Is it correct that anonymous get's
only exact hits but logged in get's hits with spaces in? Seems a little strange.

Secondly - the difference 35/36 - 39/40. The five pics that are missing in the
API are all one user's. All pics are "visible to anyone" both for him and
others. What other reasons could there be that his pics are not returned? I
can't see anything obvious about them.

I've tested this both via flickrj library and via the API explorer pages on
flickr itself.

Am somewhat confused here - any hints?