It is to give 'visual interest' for the viewer.
The real system had a linkage system interrupted by two 'gaps' - one near the cam, which was set closed by pulling the 'trigger enable' cocking lever, placing the linkages in mechanical contact with the cam follower, the other a hinged arm within the (airframe's) trigger group which used a Bowden cable from the control column trigger to pull an L-shaped, spring loaded lever into alignment with the linkage and the trigger actuator. The trigger actuator was pushed against a conventional trigger in time with the engine fitted cam, firing a single shot while the cam was in position to permit firing, releasing the trigger immediately the engine rotated away.
Each gun was also fitted with a cocking lever to clear jams and misfires, and to cycle the mechanism, but these could be hard to operate while flying an unstable fighter.
Other variants existed with cables or oscillating rods, but the Fokker synchroniser used one firing impulse per revolution (engine speeds ~1200 rpm), with around 2/3rds of the trigger activations being during the loading cycle and only around one in 3 being for a loaded chamber ~ giving around 400 rpm per gun on average - slightly down on the natural cyclic rate of the MG08 450-500 rpm.
Slight changes of engine speed/aircraft speed would result in different proportions of 1 round in 2, 1 round in 3 and one round in 4 revolutions and an irregular, variable rate of fire. This is synchronised fire.
Fokker aircraft had a basic HOTAS
- with the control stick fitted with a static right side, with two triggers (one for each gun), and a 'lever' for the left handle which 'fine' controlled the air-throttle for the engine.
Fuel and air 'coarse' adjustments were on the cockpit sidewall.