Decentralization in this case means one can secede easily from the central authority. So anyone working on a project can easily split away from the main group at any time. But every project have a clear governance where the main direction is set and the canonical version of the thing being under version control is stored.

That canonical version is altered following a process and almost every project agrees that changes should be proposed against it. Even with independent agents, there should be a way to ensure consensus and decides the final version. And that problem is a very hard one.