I mean, it's hard to say what was going on here. So, the car has $10k worth of mods? If so, I guess it comes down to if this was going to be a warranty repair. If it was gonna be a warranty repair, then the test drive makes sense. Some random, arbitrary noise that you couldn't hear in the camera. Beat the snot out of it, and if it blows up - cool, drop a new motor in it and be done with it. Or it burns away any possible carbon, and the noise goes away. If it's customer pay - ehh, then it gets a little picky, especially at a dealership with mods. This really varies by dealer, some are much more OK dealing with modified cars than others.
I also heard the tech say the owner of the car was really picky, and that might very well be the case. The noise was evidently gone at the end of the test drive, so the tech did SOMETHING right. Pain in the [censored] customers are, well, a pain in the [censored], and are going to complain about minuscule stuff regardless. Make it go away, and the customer goes home happy until they decide to [censored] about something else.