When you talk about voice its good to remember that there are two kinds of voice.

There is the author's voice which reveals the bias and beliefs of the author. It may change over time based on life experience. Sometimes it can be heard by reading a single work. With other authors, it may require reading an entire body of works to get it.

Then there is the narrative voice. That's the narrator of the tale. It can be the author and/or any number of characters. And, it can change within the tale. LL did that several times. I think "Treasure Mountain" is a good example.

But, you kind of stand the author's voice on its head when there are multiple authors. It's not that unusual for two authors to work together. But it seems like a work with 20 or more authors would almost be a little schizophrenic. That may not be a bad thing, but certainly, it would be unusual.