Question for those who are familiar with Flagship F dining

My partner is going to the US soon on a work trip, (his work company booked him in J but he upgraded to F with a systemwide upgrade).

When you have your meal and drinks in the FFD section, do you leave a tip at the end? I know the US has a big tipping culture. We tip accordingly in restaurants/bars but in the airport lounge I’m confused. From what I see, in the FFD you have someone bringing you the food and serving your drinks, so it’s waiter service..? If tip is expected or would be polite and the right thing to do, how much do you guys recommend leaving?

We also ask because he’d like to have some cash to tip if it’s expected…(when we leave a country we try to get rid of the paper currency as much as we can if it’s not the Euro which we use).