The article specifically mentions that these businesses have no W-2 employees, not that they don't utilize any contractors.
> which then opens the ongoing question of when is a contractor a defacto employee?
There are very specific IRS rules about when someone is classified as a W-2 employee vs a contractor; it's not like it's just up to the business. Of course there are gray areas (e.g. the whole "Uber drivers should be employees" debate), and there are many court cases focused on employee classification, but in general, having no W-2 employees whatsoever is a pretty good indication you are a single person business.
"He relies on a team of three virtual assistants, who are contractors, to help him with tasks like phone and email support."
More to the point some of the businesses are one employee, which then opens the ongoing question of when is a contractor a defacto employee?
Maybe the numbers are compensated by the existence of other single employee businesses who "employ" family members to spread income?