What is a drag brake? I remember back in the day brakes were never an issue, to stop the rear wheel was locked and fishtailing,never used a coaster brake enough to see if it had any fade resistance, the construction was rather simple with brass or bronze"stopper thingys" The steeper the hill the better( more terminal velocity) perhaps God makes exceptions for Low IQ, youth,DA and sometimes drunks.
OTH I do like the idea of the hydraulic caliper for the simple reason of both pads working simultanously. You do not suppose that the OP accidentally pulled a lever with a wheel off? If the seal was bypassed it may have never had a chance to reseat correctly. I am on OP's side though,I consider sub $4000 high priced.