Based on the data here, the grandparent is wrong. Maybe they were historically correct, but today the three middle quintiles of economic class is over-represent

Based on the data here, the grandparent is wrong. Maybe they were historically correct, but today the three middle quintiles of economic class is over-represented https://www.cfr.org/article/demographics-us-military https://www.cfr.org/article/demographics-us-military (Look for the graph titled "Neighborhood affluence for 2016 recruits")