While multisig was not a thing, a clever enough person could come up with a multi-sig like method at any point. Breaking a bitcoin key into two halves was always possible -- although not quite the same would work.
How would it work and who would be the person that breaks the key into two halves, unless you are talking about some software that could do it? If I break the private key into two and give you one half and keep the other for myself, how can you be sure I didn't keep your part as well. Introducing a third person to do if for us can bring additional problems. Now we have another subject who knows the key or could give me or you absolute control if he wanted to.