I would be leery of what the buyer's agent has to say. If there is a signature line on a document it was put there for a reason. I would make sure that it is signed for your protection.
Something might happen and you might bring suit in the future based on their disclosure. Without a signature on a given section they might claim that they didn't write that and that wasn't a part of their disclosure.
It may be acceptable and enforceable without the signature in California, but in my opinion never a good practice. I hope that helps.