I plant only 1 seed per pot too. I’ve always blamed it on my Scottish heritage. Last summer I found 2 plants coming up IN THE SAME POT...I gingerly and carefuly cut the pot in half and planted the beans in the molasses pot. They never realized they were siamese plants. lol
I have accidentally put two seeds in the same pot when planting maters and peppers, but will snip one of them off as soon as they come up.