A restaurant is a private business and their seating is private, I don’t believe any restaurant would be happy with some random trying to hurry on their customers.

If a customer is taking excessive time it would be up to the staff to request them to move on.

Totally depends on the venue, and how much control the restaurant staff has on the seating, versus if people come in and manage their own seating.

What I took from the original tweet was it's the latter, and not the former.

What you are describing is for the former.