It's not the signing that OP criticizes. It's that the "something" is defined by an URL whose destination can change, and otherwise none of the "something"'s co

It's not the signing that OP criticizes. It's that the "something" is defined by an URL whose destination can change, and otherwise none of the "something"'s content (like, for example a hash) is in the contract. I doubt a court would consider such a vague definition of content as "real".