It is simply an annoying deception and nothing more. Given that AS has lengthy descriptions of his service standard and even notes that its very short flights have limited beverage service, it does nothing more than annoy passengers to create a fake term which says nothing and is not defined in the service standard:

"Note: our short shuttle flights between Seattle-Portland and Seattle-Spokane offer limited beverage service."

There is nothing wrong with this statement. It is informative and lets the customer know what he will get. "Pub service" sounds like a lager with a steak & kidney pie.