Had a recent stay where I went with the "breakfast included" rate. Confirmed with the front desk that I could use my F&B credit for gratuity at breakfast. I just left a normal tip, short of the full credit, since I wasn't completely confident that I would get the credit. But when I saw the final folio they had charged the entire F&B credit to the hotel restaurant (nothing about it being a tip) and reimbursed me back the same amount. Didn't make any financial difference to me, but it was interesting.