You should have wondered, why can't your designer pal do it, if it's OK for Warhol?
The answer may have been: Warhol's process, coloring, final result, context, was way more transformative physically, and also semantically.
I think this is where we need art experts who are advising judges, it's sort of like maybe that trope where judges are making judgements about encryption and they don't understand the technology. Not assuming these judges were not art buffs, it's the SC, it's probably a very complex, refined, elaborate, and legally sound judgement...but I think they're missing some key connection to art to have gone this way.
2 dissenters thank God. Hopefully overturned in future, or further refined to protect artists and great art. I think the plaintiff here is less an artist and more a "professional paparazzi with a lighting set up".