Istanbul did rebut your ridiculous statements--at first. He now seems determined to ignore you. Writing this, I wonder why I have not followed his example in this regard...
As far as who is wrong, I have already explained that sligh is an umbrella term. I am not going to beat a dead horse.
But...
I read some book (Alastor by Jack Vance) and saw some movies (Lawrence of Arabia, The Gift, 12 Angry Men, Life of Brian, Ju-On, Jackie Brown, Close Encounters of the Third Kind, and I forget the rest).
Or did you mean the previous weekend?
My guess is that this happens so rarely that people don't really bother to distinguish between the two just for semasiological purposes. I've checked regular dictionaries, and none mention anything about uteruses in the definition for "twins." But I think a medical dictionary would be a much...