With the added 'bonus' of circulating passengers past retail opportunities.
I'm sure it does, though some retail opportunities can be put on platforms - at least in some stations. But what were the alternatives at BHM?
I suspect the reason the design came out like that was much less cynical. Early in the design you ask yourself "where are passengers going to be waiting?", so as to work out what sort of environment to provide. In this case, you might well conclude that there is no point even trying to make the platform level the kind of place anyone would spend time by choice. Just providing enough space by modern standards might be difficult (and that probably goes for large stations in general). So you plan the layout, passenger flows (now a major factor in the design process), and yes, retail, on that basis. Though that may not fully explain some of the routings between platforms.