They did implement pre-emption at some point and there are parts of that still in the code. It's intended to let you more easily manage load e.g. by de-scheduli

They did implement pre-emption at some point and there are parts of that still in the code. It's intended to let you more easily manage load e.g. by de-scheduling complicated batch jobs that are low priority and then re-scheduling when the service is under lighter load. But it won't ship as public API as a part of Loom, maybe it will never ship (generally once OpenJDK finishes a project it gets de-staffed and they don't go back to it).