Selection of members is believed to be largely the result of high-level deliberations among incumbent members of the party's Politburo and PSC as well as retired PSC members. Prospective candidates for membership in the PSC typically rely on individual members of this high level group to act as their patrons. The current and former Politburo members conduct several rounds of deliberations interspersed with a series of straw polls to determine their support for the candidacy of new Politburo and PSC members. These straw polls are not binding and instead a reflect the evolving consensus of the group on a new member's candidacy. The Politburo may also conduct a straw poll of all incumbent Central Committee members on the candidacy of new Politburo and PSC members, but this poll is only consultative. The process of selecting the new Politburo and PSC begins with a closed door session of the incumbent PSC at Beidaihe in the last summer before the Party Congress convenes in the fall. The list of Politburo and PSC candidates for the Central Committee to formally confirm is usually complete several weeks before the Party Congress.[8][9]
https://en.wikipedia.org/wiki/Politburo_Standing_Committee_of_the_Chinese_Communist_Party
Why is the selection process of the Politburo Standing Committee of the Chinese Communist Party held secret? Is there a particular why they wouldn't be fully transparent on how the members are selected? I am wondering, because no one would think that the deliberation process is democratic since China is not a democratic country, so they would be no harm in admitting that the process isn't democratic, so why isn't there some kind of official document that describes how the Politburo Standing Committee of the Chinese Communist Party select its members?