My impression is that he went to the ChiComs first, they decided his stolen files were too hot for them to handle, so he went to Russia as a backup plan.
Maybe Snowden really hadn't anything with him in Hong Kong which he hasn't already shared with Journalists and the Russians.
Hard for Snowden to say no to those demands at that point. "Give us everything you have right now and we won't send you back to the US."
China does the same for any equipment or planes they seize from the US- inspect the hell out of it and then return it.