The armed forces brought that nonsense in in the 90s. I think >27 was the rule. 30> could get you kicked out and they actually did kick some people out over it. I think they got rid of it for just the reason you mention. While it is broadly accurate people should be judged on their own.
I often see the figure 30 as the threshold of obesity. Doesn't it vary with different body structures? Would people with heavy bone and muscle structure score higher without necessarily being obese?