You must have an awful lot of time on your hands. You might starve if you keep giving up your seat in a restaurant.
Re-read the story. They were sitting at the bar, not at a table in the main part of the restaurant. If they were seated at a table I would see this differently. But, that’s me. When I take a seat at the bar, order a drink, and peruse the menu, it’s on a temporary basis while awaiting my table. The article doesn’t get that deep into detail, but one could assume these two “gentlemen” were doing that very same thing. Standing while awaiting a table is not a problem. I’ve done that many times. No, I would NOT give up my table after being seated - that is, unless it was for a wounded veteran.