True. But whether it holds up in court or not is a different matter, but they agreed. And contracts do not need to be signed to be valid and enforceable. Handshake deals and verbal deals are just as valid and have indeed held up in court (even on cases worth more than a hundred million dollars). The issue is that without signatures contracts are very difficult to prove and thereby rarely hold up in court unless e.g. there are witnesses, or statements made in reference to the agreement etc, which can serve as proof.