Mazda overservicing

At the 4-year service, when my Mazda had only done 15,000 km, my service guy recommended about $300 of extra work on the vehicle, such as injection cleaning, which is not in the Mazda service. I was a bit shocked and asked if he was aware the car had only done only 15,000 km and that I was surprised they thought this work was needed. He then said no, and I asked if he had even bothered to look at the vehicle, and he said no. I then asked if he was a mechanic and he replied no. Is this over servicing, or is it genuine work needing to be done on my vehicle?