Well I'm not sure what they mean when they say "a loosely distributed checkpoint alert system" but I'm guessing it's some sort of decentralized checkpoint system, which might be a plausible solution to the Secret Chain Attack. We could release a new checkpoint hash each week but then users would have to trust our decision about which chain is the right one and that could introduce an unwanted level of centralization, which is why a decentralized or "distributed checkpoint alert system" could be an interesting solution. But when they say "loosely distributed" it gives me the impression there's still some level of centralization in the Monero checkpoint alert system. There doesn't seem to be a whole lot of technical information on how it works.