I get the feeling it’s something like this story. (stolen shamelessly from memory from a 1980’s Reader Digest)
Susie always used to pull out cans and turn them over and open them from the bottom instead of the top. She used to do so because her mom used to.
One day her husband asked her why she did it. When she stopped to think on it, she didn’t know why. So she called her mom and asked her.
Mom said, I did it because Grandma did it. Susie called Grandma.
Grandma laughed and said, we used to keep the cans down cellar, and dust would build up on the top. I was too lazy to dust them off, so I would just turn them over to use the bottom.
And thus was a tradition born.
I think several somebodies along the line got the idea that overcooked veggies=safe veggies, then just passed it along, to their children, their friends and family, and no no one knows how to cook veggies just right.