It doesn't matter if a million other people are wrong, your dude likely will be off by 10x minimum.

But also look at his own paper and he shows a "4 month lockdown" flattening the curve. (It is Figure 13 of his own paper), and obviously in that model we don't overwhelm the healthcare system, which will lead to fewer deaths.

But the main thing I think the professor is getting wrong, he discusses as if exposure and vaccine are the only option we have against CV-19 in building herd immunity. With the lockdown we are hoping to test medcations, develop IVIGs, and of course hope that post-lockdown the Late Spring and Summer months continue to show decreased severity of pulmonary disease and death.
www.n c b i.nlm.nih.gov/pmc/articles/PMC5965040/

Plus in the warmer climate viral infections have fewer bacterial co-infections and complications (due to fewer bacterial infections, and there is concern in my neck of the woods of creating antibiotic resistance with long term antibiotic use in large numbers of intubated patients with both COVID + bacterial infection).

Honestly reading the paper, I think the dude could legit be brilliant and likely he is smarter than me, but I think his conclusions are off as his analysis tends skip the major concerns and inadequacies in our healthcare system and potential improvements.