The difference between military and civilian-trained pilots is NOT simply because we let there be a difference. I am not a military-trained pilot, so I don't have a bias here, but it just seems common sense to me...But to say there's no difference in ability between someone like him and a 22-year old Lieutenant is just being disingenuous.
I'd say the difference between the 65 year old civilian GA pilot and the 22 year old Lieutenant is the same between the 16 year old whose parents can afford to let him fly even though he doesn't have the drive and the 30 year old who is working doubles and pinching pennies so he can fly every opportunity. The one who is motivated to train and genuinely cares will train to and above the standard without being dragged kicking and screaming. My instructor has a student who owned his own 172RG and took 75+ hours to get to his Private checkride while another student started his checkride at 40.5 because he was driven.
Bottom line, I think it is partly because we let there be a difference, but there doesn't HAVE to be. Like was pointed out before, unmotivated military pilots (while unusual) wash out and the ones who remain are committed. In the GA ranks, we don't have the wash out option, just the "push it back" option. Spreading that PAR out over 2 years as opposed to a few months doesn't develop the same consistency or accuracy. And while that 2+ year pilot might meet the standard, the guy who gets there in a few months and wants to have his IRA and CSEL in 18 months is going to go above and beyond because he sees the end goal.
My how we've gotten away from the original topic, so let me tie back in if I may, that motivated, driven pilot, when he gets to his AMEL or CMEL is going to WANT to be as proficient as he can be because he probably plans to go further to CMEL, MEI, ATP, etc. In that case, it doesn't really matter what you test on the checkride, he'll want to train above that standard.
On the flip side, the "just get by" student will be just as unsafe if you jack the standards up because he's only getting JUUUUST enough skill development to get him past the DPE without really caring about the real world implications of those skills. I realize that this may be a generalization, but I think by in large, it is a valid generalization.