The Predator drone is American and used the 914F. The 916iSc is used by a European agency (I guess since EASA has the type certificate but maybe that's just because it's an Austrian engine) and they don't use drones as much as America does, plus new American drones use a turbofan engine. My guess is that some government agency needed a certified engine and it was cheaper to ask Rotax to modify their engine to add a little more takeoff power instead of building an in house one and certifying it.
In the EASA type certificate documentation the only difference is that it has higher takeoff power at 5800 rpm, a little bit different dimensions for the exhaust system, and higher critical altitude. Stroke, bore, displacement, weight, and compression ratio are all the same so whoever bought this pretty much bought a bunch of paperwork to get it certified and a tweak to increase power at WOT (probably a small change to the turbocharger control software and maybe some other small changes to handle slightly higher boost pressure). Drones get long enough runways so they don't need that high takeoff power and the military ones fly usually at lower altitudes so they don't need the high critical altitude. New American drones are too heavy to use piston engines.
But it's still just a guess for me because it could be anything and Europe doesn't do drones like the US does and doesn't have the same military culture. All we really know is the public specs, that EASA has the type certificate, and the fact that it was purchased by a government agency. Could be drones but it may not be (I hope not).
