No, I don't think that shadowing works.
The problem I have with this learning technique is that the learner has to speak at the same time with the native speaker. I strongly believe that the learner needs to be able to hear her or his own voice when mimicking the native speaker.
Instead, copy the voice right after the native speaker to better mimmick it
Here is professor Alexander Arguelles who had arguably invented shadowing as a learning method and I am willing to give him the benefit of the doubt because he speaks more than a few languages
go to 10:10 to hear prof. Arguelles demonstrate his method
an now the most watched video about shadowing by one Julian, who I'm sure has never tried shadowing in his life
here is a video of Julian speaking Japanese.
There is no way he can shadow a native Japanese speaker ...