Antecdote (i.e. two people) doesn't equal fact. I stand by my opinion that the high cost of the OP school could have affected his chance of getting the scholarship. And I'll add my own antecdote.
I applied to all three branches of ROTC out of HS, Nat'l Merit semi-finalist, Senior class president, 4.1 GPA, IB grad, etc and didn't get picked up by AF for a scholarship to Duke. I did get picked up for a limited 20,000/yr scholarship from the Army. My AF recruiter said he wasnt surprised, he explained that selection for high cost schools like Duke was lower bc they just weren't a good deal for DoD-- they could give multiple level one scholarships (or whatever the term was) for the scholarship that would've been necessary to send me to Duke. I know that for MPH degrees for Flight surgeons, its the same way. A few high cost slots and then low cost slots. I can't see why HPSP would be any different. Congrats to you both on getting the scholarship but simple economics makes sense, the military can get at least two people with an 8yr contract for what they are paying for each of you individually-- undoubtedly making the cost of VCOM a factor that may've hindered his selection. But I also agree that there may've been other personal factors as well... At any rate, like I said before, those of us that got the scholarship may not really be the lucky ones after all...
