“I always do the dishes” usually means “I remember the times I did.”

Memory keeps the work you did and loses the work you did not see. Your own effort comes with the whole experience attached, while somebody else’s happened while you were out of the room, so an honest count from inside one head is always lopsided. Two people in a house can each believe they do most of it without either of them lying.

Try counting for a week instead of arguing from memory. A list on the fridge, or naming who did what each evening. Then split what is left on purpose rather than by whoever cracks first.