While that may hypothetically be the future, that time is not now. The case before the court is much more consequential in nature and may remove the need for partnerships between companies like OpenAI and ShutterShock for consenstual sharing. It must be adjudicated based on the current capabilities, facts and circumstances of the case. Does IP and copyright go out the window because computers happen to be good at taking in and transforming like a human? The complaint isn't hiding the implementation, they explained it in a high level reasonably well. US courts are some of the strictest when it comes to IP, largely in part because strict laws were passed by the legislature. The court's job is not to legislate from the bench, but adjudicate violations of the laws as they are written today.

Just because it's easy to speed on a road and other people are speeding and they aren't charged doesn't mean you can't be held liable for speeding if you're caught. Likewise, copying proprietary source code from another project into your own commercial software can seem innocuous until you get hit with a lawsuit. You "prove" it the same way you prove any other thing before a court. The jury/judge doesn't need to be absolutely certain that something did or did not happen, just that the plaintiffs prove it beyond the standard of proof.

So yes: we may as well enter a point that computers are virtually indistinguishable from humans in generating "novel" things, in that case the existing laws would need to change. In the meantime, I don't view AI models as a trump card around copyright/IP. If everyone else is following the rules of the road but you decide to stick it and do your own thing, don't expect to ram your way through without consequences.