I don't think the comparison is trying to describe the Vietnam War's impact in terms of body count, but instead to describe the pandemic's impact in terms of an

I don't think the comparison is trying to describe the Vietnam War's impact in terms of body count, but instead to describe the pandemic's impact in terms of an enormous societal issue, which IMHO it is. People have a hard time with large numbers (remember Stalin saying one death is a tragedy, 1 million is a statistic). So having markers to help with comparison is normal.