In all of the other cases, it can be deceiving, but what is deceiving in synthetic music? There may be some cases where it is relevant, like when imitating the voice of a famous singer, but other than that, music is not "real", it is work coming from the imagination of its creator. That kind of thing is already dealt with with copyright, and attribution is a common requirement, and one that YouTube already enforces (how it does that is different matter).