Agree. Unless technicians are trained in the art of sales and customer experience, they should only have a simple conversation with a customer. Leave the sales and technical questions out of it.
Years ago, I had a tech road test a car with a customer for a noise on turns. On the road test, the tech said, "Oh, I hear it, it's the left from wheel bearing, I have done tons of them. Should take under an hour to replace. And those bearings are cheap too."
I learned a valuable lesson that day!