[Zope] Adding a Factory results in a new ZCatalog index type

hello, zope is really great, but sometimes i don't know what to do.... ;-) when i add a new product through the zope management interface (call it myTest for example) and then add a new Zope Factory in this Product (with the "Add list name" something like TEST), "TEST" will be also listed in the "Select type to add"-list of the Index-Tab in a ZCatalog... I've tested this on fresh installations of 2.4.3 and 2.5.0b4. same results. i think i must do something with "filtered_meta_types", but i don't know what. can anyone give me clue? or is it a bug? greetings, mjablonski.