That is untrue, which you can tell from the simple fact that lots of stuff broke on JDK 9 even though none of the access control restrictions were turned on yet

That is untrue, which you can tell from the simple fact that lots of stuff broke on JDK 9 even though none of the access control restrictions were turned on yet, while far fewer applications broke in JDK 16 or 17, when we finally turned on the access restrictions by default. That stuff broke because of non-portable libraries shows there was a very legitimate need to stop libraries from making applications non-portable without their consent (and there are other motivations: https://openjdk.org/jeps/8305968 https://openjdk.org/jeps/8305968).