I don't think Gaiman is simply pointing out that there is no contractual resource, I think he's pointing out, in part at least, that there's no point in trying

I don't think Gaiman is simply pointing out that there is no contractual resource, I think he's pointing out, in part at least, that there's no point in trying to hold someone in a creative endeavor to a commitment of this type, at least not if you don't want the quality to suffer as the process simply doesn't work like that. People in technology are very keen to point out when people don't understand how our processes work and when they're asking us to work in ways which are counter productive. This feels to me like a writer doing the same, essentially saying, I understand what you want, but please understand that the way you want it to work isn't going to get you the result you want.