Generally coppers will defect anything if you're driving like a ding dong.
The police can slap a defect on anything, even a brand new car. It then becomes your responsibility to get it over the pits to prove them wrong, at your expense of course.
I generally find they leave you alone though if you aren’t a complete dick and if they do pull you up your attitude normally goes far.
I got pulled over last year on my motorbike for a licence check and RBT. It had an illegal exhaust on it (anything more than 10dB over stock is illegal here in QLD if I remember correctly) they didn’t have anything to say about it other than “nice bike”.
They did have a quick look at the exhaust and I don’t doubt that they would of been aware of its illegality as they would have heard it when they were pulling me up. Maybe they would have dealt that card if I was a dick to them but I wasn’t. Probably helps that I’ve got a clean driving record too.