When the Search Settings are set to 'Add Section Information to Product Text when Indexing' then all products in a section will be listed if the search criteria is found in the Section Information.
To prevent this, select Settings | Search settings | Search Options and uncheck the field 'Add Section Information to Product Text when Indexing'.
To prevent this, select Settings | Search settings | Search Options and uncheck the field 'Add Section Information to Product Text when Indexing'.