Manual flight with autothrottle/ thrust is not a good idea, and I do not practice it, neither does my company. either all ON or all OFF. combining makes things jot only more complex, it confuses both the aircraft and the crew.
It seems more and more likely that this is one of the contributing factors.
Over and over, I see Captains and FO's blindly relying on the autothrottles, never putting their hands on the thrust levers to feel their reaction ( Boeing here) or at least monitoring the thrust trend and value ( on AB).