Grandparent can still work off their local git repository, create local branches and commits, unlike the traditional VCS model which required branching and commits to be immediately synced to a centralized node.
The centralization issue that you raise is a different one; most projects intend to take contributions from folks and merge them into a single product.
Noted on the definition of the word “decentralized”, but the comment I was replying to was specifically about the ability to “send/receive code and patches”, that’s what I haven’t seen done without a central sync point.