Honestly, never came across official statement that says Flight is "civilian only". Neither have I ever found one about MSFS and X-Plane. But at least we all know they're designed as civilian flightsims. IMHO, it takes more than DLCs to make a military sim out of Flight (and MSFS and XPlane, for that matter). They have to consider things like, most importantly, weapons ballistic, AI (pilots, missiles, etc), damage modelling and campaign, among others. VRS did a great job bringing F/A-18E and all its weapons and enemies to MSFS world. But not enough. Not even close. I never use it for anything other than carrier qual and air refueling "missions".
"It ebbs and flows, shipmate. A hot woman and a cold beer will put all this in proper perspective."