I've had a few similar situations. Three of them actually just during my last deployment.
I was in the gym and ran across some Army dudes doing some grappling, so I approached them, introduced myself and asked if I could join in. At this point I stressed to them, (and again I'll stress to you) that I am a novice at best. I'm a white belt in BJJ and only have a couple of months of very sporadic training under me belt. The both told me that they were Army combative level three certified (there are four levels I believe). I was really tentative for the first 15 seconds or se during the first roll before realizing that this guy had absolutely no clue what he was doing. Within 5 minutes it was painfully clear that these guys had been pushed through some completely bullshit course, given a certification and told that they were killers. It was honestly shocking. I'm Air Force and had never trained with any other branches on the mats and was expecting a lot more. After a few rolls these guys were floored at how good they thought I was, and I couldn't bring myself to tell them that I'm actually not very good at all, it was just that they are terrible.
Then they told me that I needed to meet a buddy of there's who was a Marine and a BJJ Brown belt. Like an idiot, I got my hopes up that this guy would actually know what he was doing and that session went even worse than the one I just described.
I really wanna stress that I am a WHITE BELT, and at the time I knew no BJJ other than what I had seen on Youtube and practiced with some buddies. So the next time somebody tells you about how badass they are due to there branches combative course, that it with a grain of salt.