I do not want to speculate, but could not do it Chinese on purpose? For example to gain some info about Japanese "rules for engagement" for situations like these?

I'm not so sure the Chinese pilots were under orders or not.  Remember that incident when a Chinese J6 collided with one of our P-3s in 2001?  The Chinese were performing dangerous maneuvers around the bigger plane and paid the ultimate price for it.  Of course, this led to a windfall of sorts for the Chinese; losing an obsolete fighter for whatever they gleaned off the sophisticated P-3, but I doubt if that was the purpose of the action because it was nothing short of a miracle that the recon plane did not crash as well.  I think that Chinese pilots are trained to be arrogant SOBs, which makes them difficult to control and potentially as dangerous to their side as ours or any others.  Bad discipline is bad policy, and stupid pilots eventually kill themselves stupidly.

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