Do the UR-C interfaces have bidirectional power via the USB-C port?

It looks to me like all the UR-C interfaces, even the smaller bus-powered ones, have the option to be plugged in to a separate power adapter instead of depending on the USB-C port for bus power.

What I’m wondering is if the interfaces will charge a connected device over USB-C when plugged in via separate power adapter. That is, if I get an iPad Pro, can it receive power to keep its battery topped up from a UR-C series interface?

No, they do not.