Some of the actual metal treatments certainly have merit as far as extending barrel life but these often change the steel structure in the actual barrel steel which makes the Bore often harder and more resistant to heat cracking and errosion.
any topical bore treatment or bullet treatment i shy away from. But again realize, i am a rifle manufacturer, if i recommend something to a customer that goes against the barrel manufactuers recommendation and something goes wrong, that is now on me, as such, i follow the recommendations of my barrel makers and pass that onto customers.
i have never been dissapointed with a top end barrel with a properly cleaned and maintaned barrel with no treatments. But again, i admit to being pretty old school.
have tested most of them just so i have some experience and will say most do nothing. Some offer minor improvements, some have some significant drawbacks. Again, i like a clean naked bore!!