Didn't know there was advanced stuff like that which could be done.
It's not well documented on the IceTV help. The IceTV Customer Support page
Using Series Recording, Favourites, Keyword Recording and Keyword Favourites is out of date and doesn't mention the search restriction tags.
It says:
By default, searches only match keywords in the show's title.
As you experienced (and I just tested), the default keyword search is over more than just the title (edd below for what other documentation says that it searches over).
The Customer Support page
How Do I Set a Preference to Record Shows of a Certain Type or Genre? refers to functionality that no longer exists (and I think that the :Using Series Recording ..." page may be referring to this same functionality.
There is one place where I've found a list of tags that you can use to narrow searches. One of the Developer pages,
Keyword Pattern Matching.
The search tags are:
"title:"
"series:"
"episode:"
"desc:"
"genre:" If genre is not found in the database this entire string is skipped
"actor:"
"director:"
"repeat:" Value can either be "yes" or "1"
"year:"
"after:"
"before:"
"lang:"
"country:"
The developer documentation says (in contradiction of the "Customer Support" page):
If no qualifier fields are set then the MATCH_STRING will match to any of the following fields:
title
series
episode
desc
genre
director
actor
country
lang
How accurate any of that is is anyone's guess, but it's the best I could find.
Note that the developer page I linked to is now described by the pages that are supposed to replace it as "legacy documentation [that] will be available for a period of time." However the new documentation doesn't have any information I could find about how matching works. The demise of the legacy documentation has foretold for some time now, but fortunately no-one has decided to remove it yet. The legacy documentation actually vital for any development work on IceTV, because it contains much more information than the documentation that's supposed to replace it.