I'm trying to understand how an oscillating sprinkler like this, is able to change directions. Does it still use a four bar linkage mechanism like a traditional oscillating sprinkler?
Most mass-produced devices have utility patents on them. I was able to locate the one (or a very similar one) for your device: EP19970306109
"By pushing the arm 19 in one direction the rocker member 17 is moved to the position illustrated in Figure 8 in which the inlet 15 is open to enable water to enter the inlet 15 whilst the inlet 14 is blocked by the member 17..."
"When water reaches the impeller 8 through the inlet 14, the water flow drives the impeller in one rotational direction and when water reaches the impeller 8 through the inlet 15 the water flow drives the impeller 8 in the other rotational direction."