I can't read the mind of the article's author, but usually in these types of articles about micro-whatever you want to stress how horizontal teams/libraries/ownership is to be avoided, because people "default" to having them, and you have to fight tooth and nail to make them understand it shouldn't be.

But for micro-FEs, there's a few things that, IMO, are unavoidable. A design system implementation (keeping its components as "dumb" as possible, no server api dependencies of any kind, no opinion about frameworks beyond the component technology it uses) is one of them. A few very very core things like authentication is another, as well as how all the routes glue together. There's a few more (nav, service workers, etc).

It should still be avoided unless absolutely impossible to avoid or if the benefits are overwhelming.