Coronaviruses in general, including the original SARS-CoV, do indeed have proofreading enzymes, which is why their genomes are so unusually stable (and hence so unusually large) for RNA viruses.
I didn’t dig down on the SARS-CoV-2 genome yet (I only started looking into this in depth yesterday) but a quick search suggests that the proofreading exonuclease is indeed there.
Coronaviruses in general, including the original SARS-CoV, do indeed have proofreading enzymes, which is why their genomes are so unusually stable (and hence so unusually large) for RNA viruses.
I didn’t dig down on the SARS-CoV-2 genome yet (I only started looking into this in depth yesterday) but a quick search suggests that the proofreading exonuclease is indeed there.