I don't get it, why would it be correct not to king them, and then immediately king them? If you want to hide that you have them, you wouldn't king them at all.
Edit: I guess you might have two that you want to king, and possibly one more that you don't want to play at all, but you don't want to reveal that you have it, and you're playing online where there will be a noticeable pause if you can king it but choose not to - in that case, to preserve the mindgame, you also have to do it in situations where you don't have the third card. If that was your answer, then I should add that it's not about online time tells, or mindgames, I believe there is at least one legitimate edge case which you might see in an IRL game, or against a bot, or both if that were possible.