I do not exactly know how network licenses work at the moment but you cannot have SU free and Pro installed on the same computer. They are practically the same program - with some additional tools for the Pro version.
So I guess it would be a tedious workflow keeping to install/uninstall the two versions.
Previously, if there was no available license on the network (or even single installation of the Pro version), it fell back to the free version making it an ideal tool for such offices as they only needed to buy a few seats. I guess this is exactly why they changed this behaviour - to encourage sales...