I was out sick for a couple of days so I could not answer.
@Ray, I am using the latest and greatest CAS 6.2 release. And I do not recall in which RC but at some point it was decided to switch from camelCase to kebab-case. That is why it is cas.service-registry.json.location in my case.
@ste, so you are facing the same issue. Are you sure about the Spring Boot behavior? I just tried it (Spring Boot 2.2.8 as CAS 6.2 is using it, too) and it works at least for the server.port property:
java -jar ./build/libs/demo-0.0.1-SNAPSHOT.jar --server.port=8080
I set it to 8081 in the application.properties and override it via command line parameter. And that's also what I understand from the Spring Boot documentation.