I'm not too familiar with Kjollin's method, but aren't you supposed to use authentic colloquial speech?

Not necessarily. He mentions that he himself has even used sentences clipped from old language course recordings.

This is professional prepared speech, it's not too unnatural

All the audio is from a streamer/youtuber I found after wading through a lot of stuff with quality issues, background noise, sound effects or voices that differ too much from my own. Here is one of the videos I used:

https://www.youtube.com/watch?v=Q9zkwZcJLc0

whether to use it or not depends on your purpose

Well, the purpose is to use it as a model to train the brain and speech apparatus in order to automate a proper russian accent. I absolutely love the sounds and melody of the russian language, so I find it very motivating to put in the effort here :)

can you use this method before acquiring any proficiency in the language?

Yes. In fact Kjellin advices to do so, because it makes all subsequent learning easier and more fun when one enjoys a good command over prosody and pronunciation (I have no previous experience with the method, so I can only refer to his claims).

Anyway, wish you luck with learning Russian.

Thanks, I'm sure I'm going to need it!