They don't go back to China often. The money will accumulate in bank through direct deposit methods so it is easy to surpass $10,000.
So if the tax treaty starts $10,000, so their retirement account should report monthly/yearly income?
I think it is due to their previous hard work in China and not have any business relationship with US of A. Also it is like pension in USA, why they need to pay 15% tax to USA just because they have Green Card?