Boston, like Atlanta, saw something in Park they liked. But apparently Boston was not so enamored with Park that they needed to keep him on the 40 man (like they keep doing with Ort for some reason). So they DFAd him, probably hoping he’d clear waivers.
Atlanta also liked Park, and probably about as much as Boston. They might DFA him for the same reason Boston and Pittsburgh did.
A few years back, there was a pitcher named Sandy Rosario who was DFAd and claimed maybe 7 or 8 times in one off-season. Teams liked him, but they didn’t love him…