Chinese being ultra-strict on US-bound flights with the extra gate area check and confiscation of liquid drinkables. I've had them claim it's a TSA requirement. The Chinese don't normally do this on flights heading for most other international destinations--for those, you may purchase bottled water/drinks in the secure airside area and take them on board, no secondary gate security check. BTW, China is not the only location in Asia where the airside water snatch-and-grab is done for USA-bound flights.