New policy or CC improvising?
New one for me today. I was sitting in row 27 on A321Neo and put my tablet, headphones and bottle of water into seaback pocket.
Cabin crew member performing checks asked if those are mine and said that nothing can be in pockets during take off and landing as it's a trip hazard in an emergency and everything must go overhead.
I was surprised because it hasn't happened before but I wasn't going to argue.
Instead I suggested that I'll hold the items in my hands and will start a movie after safety demo, but this wasn't allowed either, in an emergency I would drop the stuff and they will become a trip hazard. Kinda makes sense though.