I've always looked at this 180 degrees the opposite...
Take for example A2G Radar:
The sim engine knows where the player's jet is located and it also knows everything around the jet. The terrain, the objects, coast lines, rivers, etc.
To simply generate a display in the cockpit using all the known 1s and 0s is probably not all that difficult. In my mind, this would be "Emulating" A2G radar where you can present the player with a general picture of what is in front of the jet.
Now on top of the above, throw in all the vagaries of period-specific electronics, weather, operator error, false echoes, side lobes, "birdies", etc. and NOW you're starting to get into "Simulating" A2G Radar which includes all the imperfections and limitations of an overall system.
I suppose it's just semantics, but that's how I've always approached the concepts of Emulation Vs Simulation.
Just to take it to DCS specifics:
The A-10C is closer to simulation while the Flaming Cliffs F-15 can only emulate what the Eagle can do.