“RU-486 works by blocking the action of the hormone progesterone, which is needed to support the development of a fertilized egg.” (From https://www.britannica.com/science/abortion-pregnancy )
The pill works at times by thinning the uterine lining, which is needed to support the development of a fertilized egg.
You can talk about what changes have or haven’t taken place in the body of the mother, but these are the same thing, just accomplished by two different means. We have other means as well.