When does an espresso stop being an espresso?

Guy in front of me in the queue at the Costa coffee kiosk asks for an espresso. Girl behind the counter puts freshly ground coffee in filter, and makes an espresso. She puts it down in front of him. He looks at it then asks her to top it up please - he expects a full cup of coffee thank you.
She is slightly non-plussed and asks if he wants it topped up with hot water?
No - more coffee please - "just press the button and add some more of the same", he says.
With a well suppressed shrug, she brews another shot of coffee and tops up his cup. She brings it back and puts it down in front of him again.
"Is that OK?" she asks him.
He nods, and pays for the coffee. He picks up his coffee and starts to move away, but turns back to her.
"Where's the milk?"
"Hot or cold?"
"Hot."
She pours some hot milk into a small cream jug and hands it to him.
He nods and walks off, satisfied at last with his double strength Americano coffee for the price of a single shot espresso.