APEX REST services (created in the APEX UI) uses its own repository. ORDS REST services (created using the APIs or through SQL Developer) uses the ORDS_METADA repository. This is something that will eventually be worked out, but for now, they are just two separate ways of developing REST services. The code behind them is even a bit different, so things work a little differently between them. Both ways rely on the ORDS java middle tier component. If there is a conflict in the names, I think the ORDS built item wins (though I' not 100% sure of that).