To separate data in the lists displayed on the page "special" concept is used. Usually special can be specified like this
<inp2:p.special_PrintList/> on a template.
However this approach isn't used for products and "list_name" parameter is specified instead of it like this <inp2:p_PrintList list_name="pick_products"/>. In this case special is generated based on passed tag parameters and always used, when given "list_name" is specified.
Since In-Portal 5.1.0 concept of main list was introduced. Main list is the list on a page, that has pagination/sorting controls. It's main list, because there can be only one such list on a page. But when you have multiple product lists on a page, then their data can be mixed into a single list, when tag <inp2:p_InitList list_name="products_in_category" main_list="1"/> on top of the page.
Ready for testing.