TDA suggested rules... Rule 19: Playing the Board at Showdown. To play the board, a player must table all hole cards to get part of the pot (See Rule 13-A).Yep, it's in there & I would agree with your interpretation.
I would prefer, and think it is easier to manage, to go with - show 2 cards to win any pot.
. I have to show the
even though the queen doesn't play. It doesn't matter if I announce in advance that I'm playing only one card. Show both or GTFO. If that rule is important enough to enforce, why allow any exception, even if there's a pat hand on board?