The key slot is used to decrypt the ISN value from CAS using the ISN from key. I tested using key but that feature did not work under the beta release. I.0.3 was just release so will have to test under that release. Also tuning cannot work now until future release.
If I already have DME ISN I can run a verification check against the data read from CAS which works.
Should text latest release to see if this works now.