In fact it would be great if you could share some counter examples.
In short, you've taken a term and misappropriated it based on marketing hype. That is a reasonable thing to do when pitching to a bunch of consumers/marketing folks, it doesn't usually set all that well with engineers.
The real difference is whether than decentralized, loosely coupled system is run by and owned by a single corporation, or not.
It's the design of the system itself that determines latency, not the centralized vs. decentralized argument.
You're speaking as if twitter.com is a single giant machine on a single IP address. In fact, it's thousands of loosely coupled machines and services all working in tandem across nearly the entire globe. Sounds like a typical decentralized system to me.
I understand it can be confusing because I used these terms interchangeably as well as in more loose context, and I apologize for being incoherent. I tried to elaborate my logic throughout the rest of this thread here and there, so if you have time, please read through them.
Trust me. I do know a thing or two about the technologies I mentioned in the post.