Why? It's a basic fact that foreigners travelling in regional China are targeted for more hassle and admin than Chinese nationals, at hotels, airports, random bao'an checkpoints, entry gates, police surveillance etc. I didn't think that was contentious, but have you had a different experience?

Like I said, I'm not sure if that was the factor at TAO, but it was noticeable that in my security channel, the only 2 people pinged for secondary out of the 20 or so while I was there were were the foreigners. When challenged, the agent claimed it was because there was a book in my companion's bag, I didn't even bother asking about mine.