Recent Subaru engines must only use the factory specified coolant. It is specifically formulated for these engines. If a shop used standard Prestone, etc. at some point, that is usually where the trouble begins. FWIW, my understanding of the very newest engines is that they even more strict about this requirement. I am surprised that Subaru would endorse BarsLeak. Is this local shop folklore or factory documented? Subies are great cars, but some years had some problems in this area.
http://users.sisna.com/ignatius/subaru/headgasket.html
(broken link removed to http://suburbservice.net/how-to-service-a-subaru-coolant-system)
http://allwheeldriveauto.com/subaru-head-gasket-problems-explained/
http://users.sisna.com/ignatius/subaru/headgasket.html
(broken link removed to http://suburbservice.net/how-to-service-a-subaru-coolant-system)
http://allwheeldriveauto.com/subaru-head-gasket-problems-explained/