U can choose anything but scanner always scan everything.
The Folder selection works fine in the skinned interface version of the SUI, ashsimpl.exe, the only time where you have other folders scanned is when some also select local disks (which, you don't appear to be able to do in the non-skinned SUI, ashsimp2.exe).
So it is a bit weird that everything (local disks) appear to being scanned.
So I ran a small test with ashsimp2.exe and selected a folder, thorough with archives like yours and it only scanned that folder and its sub-folders (see image), so for me it appears to work as expected. The folder count also matches what explorer properties indicates.