Management of work, not management of people, that's the key thing. Yes there's a hierarchy of responsibilities, but individual people live many places in that hierarchy which is what makes it different.
The article doesn't do a great job conveying how Medium is actually structured. I can only speak to how it was a year and a half ago (when I left), but the difference between a system like Holacracy and a standard hierarchical organization is that a person in Holacracy might hold roles in many circles at the same time and those roles are relatively fluid.
The whole point in a role is to define who has decision-making authority over some given thing and/or what that role is responsible for. Lead links come about when a role becomes too big for a single person and turns into a circle which has its own members. The lead link is there to represent the circle to the parent circle and to determine who is filling what roles. Other than that, the circle is largely self governing (roles, responsibilities, etc are all decided in regular governance meetings as a circle, not by the lead link).
There are definitely decision makers at the company, but they're not managing people per se, they just have authority over some area of the company. The whole people side is entirely independent and generally lives outside of Holacracy.