To be fair, there's no evidence in that story that Ive even knew anything about this.
Big companies like Apple have teams of lawyers looking out for this sort of shit all the time. I'd be willing to bet that they sent out the legal notice without even discussing it with Ive.
I think Hoy and Fuchs should have told Apple to take a hike. It seems pretty clear that their puppet soundboard would, in the US at least, be considered a transformative use and probably also satire or parody, thus protecting it from an intellectual property lawsuit.
Of course, in IP law, often the most important thing is not whether or not the merits of the case are on your side, but whether you have deep enough pockets to cope with the trial. You can have all the fair use arguments in the world at your disposal, but it's still going to cost you a five- or even six-figure sum to fight the case, and when your opponent has a market capitalization of about 600 billion dollars, that's not exactly a fight you want to have.