Just going to be neutral, to be fair to the video makers, the context isnt fully there. it is written as a intiuation which means it should be a one off thing, thats all the context i know. In terms of, the only thing i see it as is a inituatiation tradtion and the person is claimed to be 12(?). I dont know what country it is, if its a child of the instructor, if its a "confidence" test just captioned as a initiation etc etc. Consent is also not covered in the video.
In terms of hitting people, the only two/three issues would be: Age,quantity and power. for quantity, by it being captioned as a inituation tradtion, it seems to be a one off thing they do. Cant comment on if they got any injuries or severty of them afterwards.
Also, i wouldnt put it down to "learning to take hits" its more of a toughness test. Many places do many diffrent things out of tradtion for if somone gets a certain belt, wants to be a instructor etc etc.
By the way DONT mark that as support for said actions, its just a neutral analysis of facts.
Just to reiterate something there, i dont know all the facts here, the only thing going off is,a apaprnt child of unknown age is goign through a 27 second blitz defence. I dont know about the teacher etc.