Update (sorta)
I forgot to look at the caliper bolts until the tow truck was on scene yesterday and loading it up. So no go there.
I also didn't have anyone available to turn the wheel while I looked underneath. Plus the sound happens only when driving, and it happens while I'm driving in a straight line. So I'm not sure that would've helped anyway.
Also, the hubs were not locked.
I did get some better views at the undercarriage though.
If it turns out that noise is just a flapping fenderwall thinger, I'm gonna be TEED OFF

(and kinda relieved)
Is this pin supposed to stick out like that?
Hopefully the Truckwerks guys will have some info for me soon.