What is the meaning of "the mouthpiece of certain power"?

On page 241 (ten pages and four in-universe years after the quoted bit), there is some discussion of God:

"... Still, so what if God exists? What's he got to do with what's right in front of us?"

"If God really exists, then he may have a mouthpiece in the mortal world."

They all stared at him for ages before the understood the implication of his words. Then one astronomer said, "General, what are you talking about? God wouldn't choose a mouthpiece from an atheist nation."

The repeated translation "mouthpiece" suggests to me that this bit of dialogue is meant as a callback to the bit on page 231, meaning that the phrase Martinsen has mistranslated as "certain power" is meant to be more like "the Most Powerful," and refer to the Abrahamic God. (See Wikipedia's list of Chinese names for God.)

Unfortunately I haven't been able to find out Liu's original phrase here, neither for "mouthpiece," nor "certain power," nor what word is being translated on page 241 as "God."

The word used by ETO members for Trisolaran high command, which Martinsen translates consistently as "the Lord," is 主 zhǔ.

On page 413, Xizi says of the droplet, "It's the tear of the blessed mother," which also seems like probably a religious expression which Martinsen has mistranslated (that is, I'm blindly guessing that the original phrase was something something 有福的母亲 yǒufú de mǔqīn, i.e. a reference to "the Blessed Mother," the Virgin Mary).

I'm not sure that any of my supposition here is right — and what is this driblet of Catholic imagery doing in a Chinese sci-fi story anyway? — but at least it's a small step that maybe someone else will build on.

Okay, according to a pirate copy I found online, the Chinese text is:

爱因斯坦说：“我考虑了很久，认为主对罗辑的恐惧只有一个可能的原因： 他是某种力量的代言人。”

Àiyīnsītǎn shuō: “Wǒ kǎolǜle hěnjiǔ, rènwéi zhǔ duì luō jí de kǒngjù zhǐyǒu yīgè kěnéng de yuányīn: Tā shì mǒu zhǒng lìliàng de dàiyánrén.”

According to my weak Google-fu, 代言人 dàiyánrén these days seems to carry a connotation of what we might call a "brand ambassador" or "celebrity spokesperson" — someone who carries and personifies an unspoken message — a "front man." I also found one instance of its being used in a legal context to mean "advocate" or "representative."

某种力量 mǒu zhǒng lìliàng indeed simply means 某 "some" 种 "kind of" 力量 "power," and is at least sometimes used with a supernatural connotation, as in the Chinese title of Rhonda Byrne's The Power, or this translation of a quotation attributed vaguely to philosopher William Godwin:

因为某种力量是我们现在观察不到的,便断言它不在人类精神的界限之内,是极不明达的。

It is extremely unjustified to assert that, because a certain power is by us right now unobservable, therefore it is not within the limits of the human spirit. [Anyone know what the English-language original is?]

TLDR: It doesn't seem to be any well-known set phrase. So it just means literally "the public spokesman for some unknown power" (or "of a certain power"). In this context, yes, it probably refers to a religious conception of God (but not necessarily a Christian one).