All of the following it hypothetical...
Did you ensure that you can actually enable jitter (not the display of jitter, but the scan for jitter) for the DX-20A3H in CD Speed? (While in the Disc Quality Scan tab, click on "advanced" and see if you can change the option to scan for jitter).
Maybe ODC has to be "set" in a similar way; I do not know.
It's also a possibility that the USB (I presume) enclosure just generically responds to the command to scan for jitter with something that won't trigger an error message with either of the scanning utilities.
Doesn't the drive just report itself as a D[H]-20A3H to everything? I the A3P worked, the A3H should be on the same whitelist to work.
I think that drive was able to scan jitter with all versions, but I cannot say for sure.