Disagreed on the "led by China" statement. I made my case against that often enough now, so I'm not repeating it here. China is a large factor still though, so if it's just hyperbolic phrasing to say that, I'm okay with it.
The volume surge on Huobi was 2 minutes ahead of Stamp. This isn't up for debate, it is there in black and white (or red and green).
Sorry, but this happens almost 9 times out of 10 and it cannot be ignored.
Arb bots are most likely keeping the exchange rates in line.