To the OP it depends on how much BP your son takes. Some is needed to break in the bat but too much will break the bat. All composites break in and get hotter. No bat company has filed for a patten on a new way of making composite bats so one has to believe they still make them the same way. That being said they will still break in. With ABI testing they have to then sell the bat below the standard to allow it to not exceed the standard after a normal break in period. Which they will exceed it after a long break in period.
Heck read the link posted from Easton. They say eastons don't need a break in and in the very next paragraph say they do lol. It's all marketing or they would have stopped being able to sell composites after the ABI was included in testing.
My advice has always been the same. Use wood in the cage.