Ok I hacked it manually. Maybe not the most elegant solution, but I just want to keep moving with my project. I did like this:
1. To check if the parent has gaze, I check both the parent’s GetHasGaze() and each child’s GetHasGaze().
2. To ignore short-term gaze losses (like when gaze moves from one child to another within the parent, or when just blinking) I moved the logic from the HasGazeChanged handler to a timer callback, starting the timer at HasGazeChanged to execute after 200ms, if the gaze is not regained.