Wild that anybody thinks simply being in the office makes employees work. I have a colleague who sits within 2m of me who keeps their (personal) phone on their desk all day. They literally prop it up against the bottom of their computer monitor. They're not even subtle about it.

They get distracted every 2-3 minutes and spend upwards or 2-3 hours on it. It distracts me when it vibrates 100+ times per day.

Boss walks in, phone is down. Boss walks out, phone in hand.