Because Media Services v3 allows an asset to have multiple StreamingLocator instances, you can have:
One ContentKeyPolicy instance with license_type = "persistent", ContentKeyPolicyRestriction with a claim on "persistent", and its StreamingLocator instance.
Another ContentKeyPolicy instance with license_type="nonpersistent", ContentKeyPolicyRestriction with a claim on "nonpersistent", and its StreamingLocator instance.
Two StreamingLocator instances that have different ContentKey values.
Depending on business logic of custom STS, different claims are issued in the JWT token. With the token, only the corresponding license can be obtained and only the corresponding URL can be played.