I believe you, trust me. I'll never forget the look on our GFC's face (a major) when we did a battlefield handover to a Marine platoon in Iraq. He asked where the PSG or PL was, and an E-4 came up to talk to him. He said "No, I need the guy that's in charge" and the young Marine said "Yeah, that's me Sir".
Regardless, I think it's taking advantage of guys. If you have that level of responsibility, you should be fairly compensated for it. Also, it screws those guys over when they get out and are competing for jobs with other guys who out rank them but had less responsibility in the service. I'm not saying all the branches need to have the same rate of promotion, and I would even agree with the argument that the Army promotes a bit too fast in some cases, but if a position is coded for an NCO, than that branch has an obligation to man that position accordingly.