They are hiding their real power.

I think the 51% we witnessed was a demonstration of power. I do not know for what reason.

They could have blocked miners as to keep their hash rates down as they did before, but they didn't.

I would say that GHash has MUCH more than 51%.

That being said, I do have some of my miners pointed at them.

EDIT: On the subject, NO, I don't believe that BTC is decentralized anymore.
In fact, the fact that we depend on the core dev team for anything means it is centralized, and from what I understand the core dev team is under the TBF orders.
Apart from that BTC mining is completely centralized.