PTSD is the easiest diagnosis to get through the VA, and thus it is rife with fraud. As a result, it is quite difficult to get anything approaching accurate or useful numbers for it.
It sounds like you're one of the ideal ones for your line of work, though; brains that are less susceptible to stress damage are rare. It's why not everyone is fit to become a police officer or give talks in front of big crowds. Others have an adrenaline sensitivity or a panic groove etched so deeply in their brains that they'll forget their names if you talk to them when they don't expect it.
I'm also assuming you entered the military voluntarily. There's a predisposition for certain brains to take on and thrive in certain careers. As a DWB friend of mine put it about the career mercs he treated, "They aren't psychopaths, just real mean sons of bitches."
You don't have to like people who aren't built as tough as you, but that doesn't mean they're faking.
The vast majority of the people in the military are never exposed to anything at all. They do a job and they get paid for it. They’re no more likely to develop ptsd than the local grocer, plumber or electrician. Many of them are exactly a grocer, plumber, or electrician with a military ID card. They’re not “Mercs” any more than the local grocer...
Everyone on active duty today entered voluntarily as well.
My nephews serve as examples. Their non-combat roles were heavy construction, setting up communication networks, and airplane mechanic. However all three actually saw combat. 2 wound up with PTSD. And one wound up seriously injured when the plane that was delivering him to a secret mission got shot down en route.
In fact according to some estimates, the prevalence of PTSD among veterans of the Iraq war exceeds the fraction who were supposedly in combat roles.