While reviewing flags in the 10k tools, you sometimes see a "Delete Answer" or "Delete Question" button next to the "Flag or disagree..." button.
Normally if you click the button, you cast a delete vote. But if the post already has 3 votes and is deleted, you can still click the button, but it then cast an undelete vote. And this is probably not the requested action.
So I think it should be better to ignore extra delete votes, because there are other channels to cast undelete votes.