I think a smarter, more devious scam is more likely than a system flaw TBH.
It's often the case that the most plausible answer is the truth. Much as the people who've been scammed would have you believe otherwise, it's still more likely that they, themselves were careless; upsurge or not.
Part of the wider issue here, for me anyway, is the message: "your SCID has expired". It's ambiguous to say the least; it doesn't convey to me that the email address linked to the account has been changed. If it was obvious that the account had been compromised, some people wouldn't go looking for alternative answers to fit their narrative.