Yes, when limiting your search to a particular Source Type, the options may refer to either Publication Type or Document Type. Some Quick Search records have Document Type, while others have Publication Type. Source Type includes both of these fields when limiting.
For example, an item in your search results may be presented as a periodical, which is a Publication Type. When you open the item record, in the field marked “Document Type,” it could be listed as a book review. Therefore, choosing either of these options when limiting to a “Source Type” would produce this record in your search results.
As an example, in this search
select the database "Alternative Press Index," then limit your source type to "Book Reviews." You should have three results which are periodicals, and which also come up if you limit the source type to "Periodicals" instead. If you open any of those three search results, in the “Document Type” field should be the phrase “Book Review.”
Unfortunately, there is no place to see all source type for a given record.
Please see http://support.epnet.com/knowledge_base/detail.php?id=5382 for how Publication Types map to Source Types.