All my bikes have been built from the frame up, or built the frame and then added components. None are similar to how they were originally sold. Its pretty easy to say 'its an updated CAAD3' or 'its a modernized 80s road frame'.
No they arent the same bikes as original. Very few bikes are, if they are used. Nobody but collectors care that they arent original and so they are still called by the original name. A bike that is used well for 2 years will have new tires, saddle, tape, pedals, chain, brake pads, and maybe new wheels too(if the user wants). Something that has so many changes just from regular use should still be called what it originally was.