technically, only MGM admitted as much
At least some of the Justices, Scalia in particular, seemed troubled by how an inventor would know, at the time of inventing, how its invention might be marketed in the future. How, some of the Justices asked MGM, could the inventors of the iPod (or the VCR, or the photocopier, or even the printing press) know whether they could go ahead with developing their invention? It surely would not be difficult for them to imagine that somebody might hit upon the idea of marketing their device as a tool for infringement.
MGM's answer to this was pretty unsatisfying. They said that at the time the iPod was invented, it was clear that there were many perfectly lawful uses for it, such as ripping one's own CD and storing it in the iPod. This was a very interesting point for them to make, not least because I would wager that there are a substantial number of people on MGM's side of the case who don't think that example is one bit legal. But they've now conceded the contrary in open court, so if they actually win this case they'll be barred from challenging "ripping" in the future under the doctrine of judicial estoppel. In any event, though, MGM's iPod example did exactly what their proposed standard expressly doesn't do: it evaluated the legality of the invention based on the knowledge available to the inventor at the time, not from a post hoc perspective that asks how the invention is subsequently marketed or what business models later grow up around it.