Guys, he's right. FNVEdit shows that LootFirstKitNV has 2 LootChemsNVHealing75, which has a 1 in 8 chance of picking LootChemsNVDoctorBag50 which has a 1 in 2 chance of returning no item.
This means that, technically, 9.2% (approx. 1 in 11) of First Aid kits should have at least 1 doctors bag
Math is below because I am far from a stats guru.
LootChemsNVHealing75 : 3/4 * 1/8 * 1/2 = 3/64 (3/4 chance of picking something, 1/8 chance of that something being a 1/2 chance at a doctors bag)
(3/64 * 3/64) 0.22% of First Aid kits have 2 doctor's bags, (1 - 61/64 * 61/64 - 3/64 * 3/64) 8.9% have 1 doctor's bag, (61/64 * 61/64) 90.8% have no doctor's bags.