Are they poking around, looking for evidence of mass detentions? Or are they complaining about how they "spent more time being frustrated, bored, and whinging about lost funds than actually enjoying ourselves" (https://www.lostwithpurpose.com/why-we-didnt-like-traveling-...)?
People disappear if they talk to foreign journalists and nosy travellers with cameras and western ideals.
2007 was a different era, a lot has changed politically in the meantime.
I posted this elsewhere in the thread, but maybe you didn't see it:
China’s mass indoctrination camps evoke Cultural Revolution (https://apnews.com/6e151296fb194f85ba69a8babd972e4b):
> At first, Bekali did not want the AP to publish his account for fear that his sister and mother in China would be detained and sent to re-education.
> But on March 10, back in China, the police took his sister, Adila Bekali. A week later, on March 19, they took his mother, Amina Sadik. And on April 24, his father, Ebrayem.
> Bekali changed his mind and said he wanted to tell his story, no matter the consequences.
> “Things have already come this far,” he said. “I have nothing left to lose.”
China isn't a western country, and I don't think you can count on being granted western-levels of freedom of movement there, especially in "sensitive" areas. For instance, I understand you need a special permit to visit Tibet, which is another province with similar ethnic tensions.
The level of surveillance in Xinjiang is so intense that the locals will often get questioned by the police about contacts with foreigners (e.g. getting a phone or skype call from abroad). The locals probably aren't eager to talk to foreigners about sensitive topics because they fear reprisal.
China also has special visas for journalists, and something tells me that that they'll deny the application if your itinerary includes areas where they don't want people poking around. If you're applying for a tourist visa, in some cases (like if you work for a newspaper) it's advised that you promise that you'll not engage in journalism during your trip. I'm guessing the Chinese will interpret a bunch of foreigners poking around sensitive areas with cameras as people practicing unauthorized journalism, put a stop to it, and maybe even deport those people for visa violations.