I'm well aware of that. I can also cite
counter examples that show the opposite. Your proof specifically mentions heating the water 2 degrees F per minute. Other examples where the frog did indeed die the water was heated an order of magnitude slower.
Regardless, I never said "As the scientific fact", I said "As the saying goes". "An apple a day keeps the doctor away", "the pen is mightier than the sword", and "a watched pot never boils" all are scientifically false proverbial sayings, yet they illustrate an underlying general truth or lesson.