I hadn't heard of it before either. Apparently, for these composite bats especially, they actually hit better after being broken in. I'm not sure why that is - I guess the metal softens a little bit, allowing for the bat's energy to transfer to the ball better...? I know I'm not using the correct terminology here and I'm honestly not sure, but that's kind of how I picture it in my head. What it boils down to though is that composite bats will actually hit farther after a couple hundreds hits on them than they will straight out of the wrapper.
P.S. Mayhem thinks we are nerds and "a bat is a bat!" Silly Mayhem...