https://www.youtube.com/watch?v=CzjsEsdmYNk
Interesting video with lots of information on Sony/Marvel deal. But skipping to to 10:43, basically:
With Movies, Sony is licensed Spider-Man characters. For the deal between Marvel and Sony for MCU, for characters put in MCU movies, Marvel gets a stake in and when deal ends those characters will be disputed/frozen from use.
For example, if they had a faithful comic book Mary Jane, Harry, or Venom in MCU, their ownership wout be disputed and the characters frozen from use as long as Sony is licensed characters from Marvel. So the trick around this for Sony is to for the MCU movies create new characters with traits of originals. This is why all Spider-Man characters in MCU movies differ from their original version so that when deal ends, Sony is allowed to use the comic faithful versions in their films because it's not the "same" character.