> Is it worse than walking around 8 hours a day listening to music? Having headphones on while washing dishes and walking the dog?

If you think about cognitive load, then I would say yes.

Listening to music or even talking with headphones does consume some of your brain power, but you are able to execute physical tasks reasonably well. For example I am able to do DIY (apart from measuring) whilst listening to audiobooks. I can do all the household chores too (washing up, clothes, tidying vaccuming etc)

I cannot do that with short videos playing. firstly I have to hold the device, secondly I'm not looking at what I am doing, thirdly, moving pictures attract my attention.

In the same way that that most people are utterly unable to do "thinking work" (ie stuff that requires inner monologue and visualisation [sorry aphantasia people]) with a TV within visual range. I know that some people are able to do ironing infront of the TV, but I'd struggle with that to do a good job