Not true, all they have to do is suspect it is a gross polluter. A small puff of black or blue smoke, stinky smell, strange engine sound etc. Has nothing to do with being smog exempt. In California smog exempt is an incorrect term BTW, your 72 240Z with a 2JZ, Rb25, SR20, LM7 or whatever can be sent in to have a smog inspection at any time.
They do not have to prove anything to you.
And go before a judge who did not get laid the night before and turn a fix it ticket into the possibility of a smog check or referee inspection?
Just fix the smoke problem and find a police officer to sign it off.
6 degrees of separation says that you can find someone who knows one that will sign it off for a few beers and some fish and chips at the local Irish pub.