I agree that there shouldn't be a compliance flag, and appreciate the need to remain compliant. I also think there should be a better approach for JPA.

I using as much JPA compliance as I can. This is the only unusual case I've run into (so far). I don't really need to use anything special except the run-time property override, so other than delivering me WAY more debug than I want if I've made an error in a change to one of my Entities, this provides me with what I need, the ability to build the connection string using run-time properties. (I'm using TLS in MariaDB, so I can't use hibernate.properties. I tried.)