I have been in possession of many AD bumpers of varying degrees of condition and finish and I don't recall ever seeing a bent one.
I have removed a front bumper which had been mounted in the rear and when it came free, it nearly shot me across the yard! So yes, I assume that they are spring steel to some degree.

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission