Sorry, it gets confusing since APM:Copter autopilot (I guess that's what they are calling it now) can run on PX4 hardware running NuttX too. So they are using the full PX4 flight stack as well?
[we have a nightmare at work trying to distinguish between original PX4FMU running PX4, Pixhawks running PX4, and Pixhawks running APM codebase in conversations]