Yes, this is scam prevention 101. Anyone who called you is always unverified. It's hard for me to take seriously a "scam prevention expert" who doesn't seem to know or follow this rule, which by itself is enough to protect you from most scams. Normally I try not to victim blame people for getting scammed, but when you've made a declaration like that you forfeit that right.

I'll also point out that the author seems to have some complicated arrangement for their phone number(s), presumably in the name of security, that in fact got in the way of identifying this to be a scam.