I don't dispute the 1.75 million year date (the oldest estimates of Homo erectus migration out of Africa is 1.8 million BC). I do doubt the 2.25 million year date, only because China is a marked distance from Africa and if Homo erectus had so expanded its range that early one would expect that it would be more readily apparent. However, I have no problem with the idea in the abstract. The Chinese are notorious for 'unsubstantiable' archeological claims..
As for the Flores 'hobbits' if they are what they appear to be from what little I know of them (a dwarf species typical of island fauna) then it seems they could very well be a pygmy erectus. Since the isolated population would've obviously experienced significant genetic change in any event, that may just as well include greater intelligence. That being said, I have no objection to the concept of Homo erectus necklace ability either.
PS. Cutest dwarf species of all: pygmy mammoth!
The only one I'm certain about are the Cr-Magnon, they had a larger brain than moderns. The jury is still out on all others.
Here's an info filled article, Human Origins, I read down to where it said that Neanderthals had a larger brain than moderns(us).Gotta do something else now, back later.