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what you've described is clearly understood as an exception to the rule rather than an expression of it if you read through china's basic policy on religion and religious practices, otherwise known as document 19 (eng, baidou page).

regarding religious policy towards the masses, it states (quoting from the english translation, but you can check the original if you'd like):

The basic policy the Party has adopted toward the religious question is that of respect for and protection of the freedom of religious belief. This is a long-term policy, one which must be continually carried out until that future time when religion will itself disappear. What do we mean by freedom of religious belief? We mean that every citizen has the freedom to believe in religion and also the freedom not to believe in religion. S/he has also the freedom to believe in this religion or that religion. Within a particular religion, s/he has the freedom to believe in this sect or that sect. A person who was previously a nonbeliever has the freedom to become a religious believer, and one who has been a religious believer has the freedom to become a nonbeliever. We Communists are atheists and must unremittingly propagate atheism. Yet at the same time we must understand that it will be fruitless and extremely harmful to use simple coercion in dealing with the people's ideological and spiritual questions--and this includes religious questions. We must further understand that at the present historical stage the difference that exists between the mass of believers and nonbelievers in matters of ideology and belief is relatively secondary. If we then one-sidedly emphasize this difference, even to the point of giving it primary importance--for example, by discriminating against and attacking the mass of religious believers, while neglecting and denying that the basic political and economic welfare of the mass of both religious believers and nonbelievers is the same--then we forget that the Party's basic task is to unite all the people (and this includes the broad mass of believers and nonbelievers alike) in order that all may strive to construct a modern, powerful Socialist state. To behave otherwise would only exacerbate the estrangement between the mass of believers and nonbelievers as well as incite and aggravate religious fanaticism, resulting in serious consequences for our Socialist enterprise. Our Party, therefore, bases its policy of freedom of religious belief on the theory formulated by Marxism-Leninism, and it is the only correct policy genuinely consonant with the people's welfare.

i.e. the masses are allowed to believe whatever they want so long as they are not forced to as children, there are no material consequences for believing in this or that, etc. notably, it states that "we communists are atheists and must unremittingly propagate atheism."

regarding ideological unity regarding atheism in the party, it states in no uncertain terms:

The fact that our Party proclaims and implements a policy of freedom of religious belief does not, of course, mean that Communist Party members can freely believe in religion. The policy of freedom of religious belief is directed toward the citizens of our country; it is not applicable to Party members. Unlike the average citizen, the Party member belongs to a Marxist political party, and there can be no doubt at all that s/he must be an atheist and not a theist. Our Party has clearly stated on many previous occasions: A Communist Party member cannot be a religious believer; s/he cannot take part in religious activities. Any member who persists in going against this proscription should be told to leave the Party.

i.e. dialectical materialism is explicitly atheist and anyone who continues to be a theist should be removed from the party. however, there is an exception made for ethnic minorities for whom all members are religious:

The present question concerns the implementation of this proscription among those ethnic minorities whose people are basically all religious believers. Here, implementation must follow the actual circumstances, and so make use of proper measures, not oversimplifying matters. We must realize that although a considerable number of Communist Party members among these ethnic minorities loyally implement the Party line, do positive work for the Party, and obey its discipline, they cannot completely shake off all religious influence.

what is the party's policy regarding these members? to allow them to be religious for the time being so as not to alienate the party from the masses, but to continue to do ideological work on these party members with the eventual goal of having them become atheists (either individually, or as an entire subgroup gradually over time):

Party organizations should in no way simply cast these Party members aside, but should patiently and meticulously carry out ideological work while taking measures to develop more fully their positive political activism, helping them gradually to acquire a dialectical and historical materialist worldview and to gradually shake off the fetters of a religious ideology.

furthermore, those with relatively lower levels of belief in religion should be prioritized over those with relatively higher beliefs:

Obviously, as we go about expanding our membership, we must take great care not to be rushed into recruiting devout religious believers or those with strong religious sentiments.

so, yes, exceptions are made for ethnic minorities that are entirely religious, but these exceptions are still relatively less religious and are guided towards atheism. the fact remains that the CPC remains a staunchly atheist organization, sees atheism as a fundamental part of dialectical materialism, and, with these exceptions in mind, enforces strict ideological unity within the party. we should follow the CPC's guidance in the west by doing the same. saying this or that ethnic minority is entirely religious and should therefore be an exception to this rule is entirely different than interpreting the exception to the rule as the rule itself. it certainly does not apply to the majority of people in the west.