Order of selected elements of a hierarchical list

The list of selected elements of a hierarchical list is given by:

$ selectedItemPosition_l: = Selected list items ($ o.hierlist.id; $ selectedItemsPositions_la)

If I select element 5, then Shift-Click on element 7, I get in array 7, 6, 5.
Not very logical! I would have expected 5, 6, 7.

Still on the topic of selection, I would like to be able to make multiple selections.
If I take the previous example, I Cde-Click on element 9, it is added to the selection; OK.
If I shift-click on 11, my selection is reduced to 9 to 11.
Not what I expect ; it is normal behaviour on finder macOS.

We need to keep in mind that clicking with a pointing device is not the only way to select items. We can also use arrow keys or keyboard shortcuts such as (shift)+command+A to select/unselect all items. There is also the question of how relevant the selection process is to the final result. Why is it important to know the exact order? Would you be interested to know if trajectory was select-a-select-b or select-a-unselect-a-select-b-select-a?

I have made a file explorer to manage pictures.
When I click on a item in explorer, I display the picture.
When I click on several elements, I expect that the last one is displayed.

I just tested in Apple Mail and I can make several multiselections with Shift Click but I have the same behaviour than in 4D ; it displays the first element of last multiselection.
Always not logical for me !