Replacement on new rotors

I recently purchased 2 new rotors for my suzuki grand vitara and had my tech install the new rotors, when I drove off… I had a shake in the steering wheel when applying the brakes and it felt like the brakes was slipping when pressing on the brakes. I took off the wheel to check for oil or dirt on the rotors and didnt see any oil/dirt on the rotors. I then took it back the tech and he install the old rotors back and didnt have the problem anymore. My tech informed me that the rotors wasnt a good set and where not balance and I needed to take them back to the store and get a replacement. Was this information correct that I was told and thanks in advance for your answer