UISplitViewController on Mac Catalyst Collapse the Primary (Sidebar) View Controller by Dragging the Split macOS Style?

So experimenting with UISplitViewController on Mac Catalyst. I have a triple split. The primary view controller is a sidebar. I have the default sidebar button showing in the toolbar and that collapsed/expands the sidebar fine. But when I drag to try to collapse the split (as is typical on macOS) the sidebar doesn't collapse. It clamps to the min. size. Is there anyway to enable this? I tried passing 0 to -setMinimumPrimaryColumnWidth: but that didn't work.