Does the Rust Rayon library have the issue the speaker was describing, where parallel inner loops mostly get executed serially once an outer loop is parallelize

Does the Rust Rayon library have the issue the speaker was describing, where parallel inner loops mostly get executed serially once an outer loop is parallelized? (I assume it does, from its Cilk heritage?) Are there workarounds for when that is a problem? Edit: Dumb mistake on my part. I was looking at the video linked in the top comment (https://www.youtube.com/watch?v=YdiZa0Y3F3c https://www.youtube.com/watch?v=YdiZa0Y3F3c) and then I came back to this thread and thought it was the topic.