cl_salv_hierseq_table get_selections issue

I'm working with the class cl_salv_hierseq_table and running into an issue when trying to retrieve the currently selected cell. Any input would be appreciated.

First I select the sales order cell at the header level as shown:

Then I press a custom button on the toolbar to trigger the "on_user_command" event. From here the cell column being returned is COM_PO_NUMBER where I'd expect it to be SALES_ORDER.

I'm quite lost as to why it's picking the wrong column, all I can think is it has something to do with the header columns being stacked.

---EDIT---

I am able to reproduce in the standard SAP program (SALV_DEMO_HIERSEQ_SELECTIONS) by changing the grid’s output so that the header spans 2 lines.

Same results.

Highlighting the top cell in the row:

When pressing ‘Display Selections’ Result is CONNID when it should be CARRID: