I think the guy is full of crap, where does it say you have to run out and get a new converter? stick the thing in there and test it already, or deal with the better business bureau and anything else you can come up with.
"Affected converters sold on or before their rescission or withdrawal date, are legal for use
and installation in California. "
http://www.arb.ca.gov/msprog/aftermktcat/catrescind.pdf
If he refuses to do the testing on a legal vehicle, I imagine you could threaten to have his ability to test vehicles for the state removed.
http://www.arb.ca.gov/msprog/aftermk...xemptcat09.pdf
Aftermarket Catalytic Converters