How important are KD jobs?

I'd love to see the general community's view on this, and please allow me to explain why...

I spent some time the past few months reviewing stats from the most recent Army Officer promotions boards (CPT/MAJ/LTC), both Active and Reserve, and noticed some interesting trends. I've passed my theory on those trends around with several others, and they all seem to think I'm on to something.

So, here's my theory: Key Development (KD) Jobs are not important for promotions below COL, except maybe the KD job of Command. Instead, KD jobs are oriented toward preventing you from failing once you have already made the promotion. In short, KD jobs help prevent falling prey to the Peter Principle* at the next rank.

In my review, the trend I noticed was that Command was the only consistent KD job that seemed to make a difference in likelihood of promotion. I already accounted for Derog and Military Education, the main promotion killers. Time after time, I saw the people who spent time making sure their file was spotless make it, often with few or even no KD jobs, and sometimes even no deployments either. At the same time, I saw people with solid awards (BSM w/"V" in one case), Ranger and other schools, and a slew of KD jobs get passed over. The main consistency was that those passed over didn't spend much time finessing their file, but just expected it to "speak for itself."

So I came to the idea that the board can't intuit KD jobs, but they can tell who worked on the presentation of their board file. If that's the case, the reason KD jobs might still matter is because it prepares you with the skills you'll need to not fall on your face in the next rank. Of course, there are other ways people can learn skills, and the jobs available in your career may have been limited beyond your ability to change, so KD jobs can't be used to rule people out for promotions (this is especially true in the Reserve, where your civilian job very well may require skills above your military grade already).

So then why the emphasis on KD jobs? Multiple reasons. For one, just because there may be other ways for you to gain the skills doesn't mean that everyone will follow them. Pushing Soldiers to get KD jobs increases the chance of more Soldiers developing the skills to succeed. For two, the original intent behind KD jobs may well have been as a promotion weeding-out method, and it just changed since then. For three, telling people that they need a KD job for promotion, rather than that it's actually beneficial after the promotion, gets people to compete and ultimately strive to shape their career while also giving commanders discretion in weeding out candidates they otherwise wouldn't have.

Anyway, I'd love to hear whether other people have come to similar conclusions. Personally, I think that if my hunch is even half-right, it's worth pursuing KD jobs as a personal development thing; promotions are just a perk.

* The Peter Principle says that within any sufficiently large hierarchical bureaucracy, people will get promoted until they reach their "level of incompetence." That is, they get promoted on past performance in their old rank rather than potential performance in the new rank, and will continue to do so until they reach a rank where they are simply no longer qualified and top out. Officially, the military tries to pretend the Peter Principle doesn't apply; unofficially, I think we've all known a handful of people who were fine in their prior rank, but simply shouldn't have been promoted.