Tree component selection is confusing

We have a use-case in SAP Lumira Designer 2.0 where it is needed to filter a main data-source based on selected region(s), which are oranized as hierarchy. Therefore we use a Tree component, set 'Selection Mode' to 'Multi' and bind it to the data-source which contains the region hierarchy. The event 'On Select' triggers the update of the main data-source based on the user selected region(s). This works fine, but we find the UI interaction with the Tree component quite confusing:

1) If the user selects a node (lets say 'Nordics') and at the same time a child-node of it (lets say 'Norway'), the filtering of the main data-source is performed for 'Nordics', because its the higher in the hierarchy. It "overrules" the also selected 'Norway'. For the user this can be quite confusing: He maybe thinks, that he only selected 'Norway' and that 'Nordics' is only marked as selected to indicate that its the parent and so helps with navigation. But in reality he could also additionally select 'Finland' and still dont see any changes.

In our opinion in a multi-select scenario the component should look different. Many known programs use check-symbols to indicate that an item is selected (or if contains sub-items, that all of them are selected) and square-symbols to indicate, that it is partly selected (which means, that some but not all of its sub-items are selected). Here is an example, how Microsoft does it:

2) Lets say the user only selects 'Norway' and select another region 'Benelux' which is below 'UK/Bx'. So he selected 2 regions and the main data-source is updated accordingly.

Now he collapse 'Nordics' and selects 'Total UK'. We think his expectation is, that 'Norway', 'Benelux' and 'Total UK' is selected, even if 'Norway' is not visible because 'Nordics' was collapsed. But when expanding 'Nordics' again, we found out, that the selection of 'Norway' was removed. But no 'On Update' event was triggered when collapsing the 'Nordics'. In our opinion 'Norway' should stay selected even when 'Nordics' is closed or there should be an 'On Update' event triggered when 'Nordics' is collapsed. But not silently removing the selection.

What do you think about our findings?

Is the Tree multi-select behaviour changeable by us?

We are very interested in your opinions and looking forward to it, thank you!