That article proves that the drama is actually about people wanting to advertise Christianity, not about practicing Christianity:

According to Zhang Wei* a local contact for Open Doors: “At times of major events like this, ministers are warned to ‘behave’, ‘be quiet’ and ‘remain invisible in the public domain’.” Pastors who are suspected of conducting church activities other than low-profile regular Sunday services can be forced to have what are known as ‘tea meetings’ with local party officials – these contain rather more threats and interrogation than actual tea.

People in China have the right to avoid religion, so you need to keep it lowkey and private. The pastors are allowed to perform the regular services, but beyond that, which it doesn't specify, but really refers to advertising and spreading the teachings to a mass audience, is forbidden. And China does have a point. People should have a right to avoid religion. If they are interested in learning about it they will seek it out. China expertly balances the situation.