Not trying be a smart a .., but they would do that how ? If for some reason one broke wouldn't it simply fall down inside the car ? Ours are one inch tube with a heim on each end. I can't imagine it coming out through the body if the heim or tube broke.
This actually is a valid question ..... the reason for this was originally intended to stop the split wishbone (or any ladder bar type) radius rod from angling downwards (under the power of the rear axle winding downwards) and pole vaulting the car - & digging up the salt in the process. While I agree that on a four link type suspension, the likelihood of a link bar ripping through the body may be a "longshot" possibility, the rules are there as written because, in the absence of a rule, most competitors would NOT put a method of limiting the travel of a broken link bar on to their cars.... it has, apparently, over the years, been demonstrated that body metal, secondary flooring, step-pans etc simply are not, at times enough to hold broken link bars back. Now, if the body was 1/4" thick steel in that area and rigidly mounted so as to, in and of itself, comply with the rules as written, you could make a valid case for the body being the retaining device. Do document thicknesses with pictures etc though.....