Well a CSV does work similar to a PRV, except that it is made to maintain cooling flow to the pump at all times. But you are right, "he had no clue" what he was talking about. The backpressure from a CSV is actually good for a pump. The CSV reduces the amp draw and makes the motor run cooler and last longer.
A 33 gallon pressure tank only holds 8 gallons of water. What is hard on the pump is cycling on/off for every 8 gallons used. Running continuously as when using a CSV is good for the pump. Pumps are made for and like "continuous duty", it is the cycling on and off that destroys them.
Contractors are being kept in the dark about this by their suppliers and manufacturers, as they see the CSV as a "disruptive product". The CSV is disruptive to their business because it is inexpensive, makes pumps last longer, uses smaller and less expensive tanks, and replaces expensive and short lived variable speed controllers and pumps. The CSV will save you a LOT of money, which is why they don't want you to know about it. The CSV will also deliver a stronger constant pressure to the house, so it is a win, win situation for you, as much as it is a lose, lose situation for installers and suppliers.
It is just a simple valve. Any plumber can install it. They just need to keep their mouths shut about things they do not understand and simply get the job done. Once they see how it works, you can usually see the light bulb above their head light up. But only on the ones with enough intelligence to know what they are looking at, which is unfortunately very rare these days.
The CSV is not a new product. We have been doing this since 1993. And as you said there would be a lot of unhappy customers if their pumps were failing prematurely. If you read our reviews and references you will see that just the opposite is happening, all those pumps are lasting much longer. The real accelerated tests are the ones where people say they never had a pump last longer than 2-3 years. Yet after adding a CSV those pumps have now lasted 15-20 years and are still working. From this you can see that the CSV actually increases the life of the pump 5 to 10 times longer than normal. Is it any wonder than someone who makes their living selling pumps and tanks would try their best to talk you out of a CSV?