Ditto - whether 'vanilla' or as an InPrivate session.
I did click the "Report this site does not contain threats" yesterday (having received an 'all-clear' on Google's report) and no doubt others did the same (with or without verification). Possibly the weight of that activity cleared the 'Unsafe' flag or maybe triggered a fresh MS scan. Or maybe a scheduled scan refreshed the site's status from SmartScreen's perspective.
Who knows - important thing is that it's accessible to all again.