A quick search shows that flu viruses are not coronaviruses. Coronaviruses are positive-sense RNA viruses, in which the viral RNA can be translated directly into viral proteins, whereas flu viruses are negative-sense RNA viruses, in which transcription via viral polymerases must occur prior to translation. It’s like in pre-digital chemical photography; the difference between a colour negative for making prints, and “colour reversal film” for slides or cine.
SARS-CoV-2 is a coronavirus, not a flu virus. This is bad news, because no vaccines have been successfully developed against coronaviruses.
I think what Node is referring to is misdiagnosis, in which particularly bad cases of common cold (caused by coronaviruses and/or rhinoviruses) are misdiagnosed as flu.
I suspect it would make more sense to call SARS-CoV-2 a SARS virus rather than a coronavirus, but neither of these are flu viruses.