As a test, I started a game with myself and one neutral AI. Events chance high. I did' do anything except building few ships. Few years in the game, AI' HW rebelled - here is a save game:
1062845567.zip
I saw AI' HW rebelled many, many times. With old file _very_ often, with a new file only very rare. I never had my HW rebelled though.
It is certain SE treats humans and AI HW differently. The disparity in events is just too obvious.