Sometimes an explanation given to a child may help at the time, but be at least partly incorrect. In order for the child to learn the (full) truth later in life, s/he may first have to 'unlearn' the original explanation. Such unlearning was not necessary for you in the case of your father's explanation of lightning,
Off-topic: Many of the grammatical 'rules' of English presented in some beginner's books have to be unlearnt later. .
Student or Learner