I had, back in the Cradle seat days (yes sadly I’m that old) a flight from BOS where Y was oversold and J undersold (F might not have been sold at all). When we were checking in at BOS the girl said WT was full and oversold. It probably didn’t hurt checking in at the Club desk with Dad having a Gold card allowing us to do so. But it helped secure seats in J and it was sooo much better than WT, even for the short flight back across the pond with WT food etc.. Girl said she’d never seen it happen before.