This is a completely unrelated issue. Microservices have nothing to do with access control. If anything, they should lend themselves to more fine grained control, but again, microservice architecture says nothing about it.
The comment suggests that just by separating things in the popular sense of microservices results in a barrier to enforce separation of concerns. That's how I read it, at least, and I find that to be is misleading.
This is the crux I see around popular discourse of microservices. It's often presented without a broader context.