The poster is saying if you are discussing non work related things it is unprofessional because you are paid to work not socialize.
If you are having a discussion with your boss don't bother him when he is on a break, book a meeting.
I agree with parent poster in large orgs but in orgs where the founder eats lunch with you that level of formalness is awkward
A company where I may not ever discuss non-work-related things sounds like a bizarre dystopia.
"I'll grab a donut from the store across the street. Does anyone else want something?" - "No, we don't because YOU'RE FIRED."
1. All work-related discussion should take place in formal meetings.
and
2. No non-work-related discussions should ever happen in the workplace.
?