There is always the risk of that, but the hardware is internal hex and stainless.Is there any concern that sliding one of the small screws over a rock will mangle the screw head to point that it couldn't be removed easily? I know that a 14MM bolt could do the same to some degree but typically, I think those bolts are generally much harder (Grade 5 or 8) whereas these small screws tend to be of a softer metal.
These were designed to be light weight and to be able to support the full weight of the vehicle and in a frontal impact while traveling through the desert at high speed.
I have a similar setup on my 200 series and 3rd gen 4runner. No issues for what I do.