UA 1414 ORD-TPA today. Typical water/OJ. Flight delayed for 30 mins. Purser Elaine came around to take breakfast and drink orders for “once we are in the air”. I clarified that this meant no pdb? She lectured that oj/water IS a pdb, it’s done now, (even though we will be sitting for another 15 mins) and there are regulations against service alcohol on the ground. News to me.