China has not banned Fasting in Xinjiang, it has banned public officials from fasting. This is very different.
The public have a right to expect public administration and services to be carried out properly and effectively at all times. Fasting can reduce the ability of a public official to correctly carry out his duties and the Chinese Government has concluded (correctly in my opinion) that the discharge of public responsibilities by its officials, takes precedence over personnel religious observances.
Yeah sure. How logical. I'm sure that's all the CCP were thinking when they announced the ban.
But could it be, that public admin jobs were sweet gigs? Could it be that if you are an Uyghur and you got a public office job, the CCP will make sure you know who the boss is?
Think back to the Manchu days. Why the hell would a Han chinese wear a queue? Oh...I know, is it because wearing one is a sign of submission and it's easy to pick out the anti-establishment types if they didn't wear one?
I would hazard to guess that this ban serves a similar purpose. If you can forgo one of the most important tenet of your religion, then you're one of the "good" muslims that can be trusted with public office.