Ultimately this. I believe the 20% came from a lower court opinion, but search sucks these last few months so I can’t find exactly what I was looking for
At the end of the day 20% different isn’t the actual standard, it’s more complicated than that. But it’s what we tell fresh developers so they have a baseline - they’re almost certainly safe at that point, and more importantly they feel safe to build things with a hard line like that
Ultimately, the supreme Court decided the case on a more fundamental level (so the % didn’t come into play at all)