When triggering a step goal in the simulator, the goal animation is overridden by getGoalView() in AppBase, but this is only working in the simulator.
To confirm that it's not just my code, I loaded the sample watch face "Analog" from the SDK and it also does not get called and the animation is the built-in Garmin step goal animation.
Note that I'm testing this on a Forerunner 955 solar.