From the science angle
It depends...
If we are talking about altered states of consciousness akin to meditation. Then from a scientific point of view—It wouldn't really apply. There is evidence that uttering "nonsense" can induce the same mental states that uttering meaningful prose induces. There are many schools of meditation that focus on uttering nonsense. (Perhaps the christian tradition of Speakin in Tongues is the most notable one, But I am only aware of Hindu and Buddhist schools of meditation that utilize "nonsense" and unlike christians—They will freely admit its nonsense
).
But I'm not sure if the above quote is in reference to practices of meditation in general (For example, comparing sikh meditation to other forms of meditation).
Or whether the above quote talks about the difference between understanding and meditating. Which I talked about in a previous post. And the futility of empty prayer over action?
(In this case the act of meditation is looked down upon even if it produces an effect because it is baseless without an understanding. And its kind of obvious how Action would be better then praying for Action)
BTW. The way in which dance and singing work is kind of like inducing sensory deprivation via sensory overload. If that makes sense? Just thought I would add to what Amarpal said.
With regards to the video
. Its safe to say that if it wasn't "working" for them. They wouldn't be doing it. But its been working for them for this long so there must be something (however small or insignificant) to it. It is not completely meaningless then. Lol
But I guess "almost meaningless" is no consolation.