Same as you as FO before I immediately removed my hand after setting the levers to Flex detent.. Common sense. I totally agree with you.
On the same subject one thing that annoys me is after V1, VR, a few guys will set their hand literally 1 or 2 seconds after I remove mine! The main gears are still on the ground.. Lol. I don’t see the point and it’s dangerous IMHO. I reckon hands on the levers should not be before at least 400 feet. I personally wait approaching thrust reduction altitude.