Shadowing is a technique for improving pronunciation popularised by the polyglot Alexander Arguelles. There are many YouTube videos about the technique; most of them don't demonstrate shadowing in the way it was described by Arguelles. A very popular example (by number of views) is Julian Northbrook's video How to improve your English Speaking and Fluency: SHADOWING.
In the YouTube video SHADOWING: Revisited (watch before you try ...), the Bulgarian language teacher Vladimir Skenderoff criticises the technique and claims that it "is mainly recommended for interpreter trainees", so it is only really appropriate for very advanced learners of a foreign language. The statement about interpreter trainees comes from a comment on one of his videos, so it does not come from what I consider a reliable source. So my question is: Is it true that shadowing is a technique for interpreter trainees? Obviously, I am looking for answers based on reliable sources.