These formats can be created by selecting in the Properties Page for the Report the Advanced Options "Enable enhanced user features in saved output version" is selected.
How can these extra formats be filtered out on an SDK code request ?
Use a search path filter.
This search path will exclude MHT and layoutdataXML format outputs:
/content/folder[@name='test']/reportView[@name='Report View of Product Description List']//output[@format != 'MHT' and @format !='layoutDataXML']
For more information refer to the chapter Search Path Syntax in the IBM Cognos Software Development Kit Developer G.