Anna-Maria Hefele has another video which I think shows this visualization even more clearly:

https://www.youtube.com/watch?v=UHTF1-IhuC0

If anyone likes overtone singing mixed with western styles definitely check out Toby Twining [0]. You can hear the overtone singing in the voice saying "reee", since that allows a rich-enough tone to produce strong overtones that can then be 'focused' by changing the embouchure (a term I'm borrowing from wind instrumentalists to describe the positions of the lips, tongue, teeth and facial muscles [1]).

[0] https://www.youtube.com/watch?v=NHtadMpziY8

[1] https://en.wikipedia.org/wiki/Embouchure

Toby was a student of Ben Johnston, who was a pioneer of combining Western Classical and American Folk music with Just Intonation. https://www.youtube.com/watch?v=_9p9L5i0MGo

We performed a piece with these overtones in highschool in 1999. Piece is called Past Life Melodies. St. Olaf Choir perfromed it in 1997: https://music.apple.com/de/album/advance-australia-fair/1567...

Edit: The overtones come later in the piece during solo parts. What you hear early on in the piece are not overtones.

Here's the full song for free on youtube: https://www.youtube.com/watch?v=Jgv6WdhbP74

Overtones begin around 4:50