I don't see much difference either. Maybe one factor in something being a Black Swan is just how widely or not the predictions are believed. There were plenty of whisperings on the internet about a potential problem with sub-prime mortgages way before 2007. I even had a lecturer at university talking about Kondratiev waves[0] and how we were possibly nearing the end of one.

[0]https://en.wikipedia.org/wiki/Kondratiev_wave