They can probably multitask better than you anyway. I can be doing work plus organising trail builds etc using my phone.
Your just scared of the young pushing you out old man. Just because you can only do 1 thing at a time doesnt mean they can.
In my work it’s all about innovation and meeting targets rather than being at a desk all day looking busy but doing f all. My old man doesn’t understand why I’m allowed to work from home as “they can’t see you sitting working”.
Times have changed in lots of cases and the workplace is one. He could be using his phone to do stuff you havent a clue about.