question

A components list is primitive feature. It collects number of items from input ports. Collecting starts by an item entering through input port one. Then a components list can be replaced by a column of a global table. This is a standard Template in an on entry trigger. After that you can update a components list only, while a combiner collects items, if you update several nodes in combiner’s attribute tree.
If you provide a sequence of different items on input port two, you must only update the total number of items from this port in components list.
Typically you associate types of items with input port numbers. But if you provide items of type A at input port two and three, you can collect them in any combination as you like. One item from input port 2 and four items from port 3 is as good as 3 items from port 2 and 2 items from port 3. Obviously you would use only port 2 and you collect all 5 items.

More than 2 input ports make only sense if you send items by their attributes through output ports of previous objects. These objects divert items to more output ports and an updated components list takes into account how many items have to enter a combiner from the input port connections.
But as shown above you can send all items you want to pack onto a container item through input port 2 only.