I was a little worried in the video by the kid wearing a sleeve. Seems like that could get sucked up into the mechanism pretty quick.
Almost by definition, you cannot presume (as a product designer) that children will be capable of thinking of their own safety; which is not the same as a parent who knows their child, making the decision to expose their child to developmentally-appropriate risk
The video demonstrating exactly that is pretty much the only thing on the linked page beside few pictures and less than 1 paragraph of text.
There are no rotating parts in the OP tool
And if the oscillation strokes are short enough it can saw rigid material while just vibrating jiggly flesh (this is how the saws used for cutting off casts work). Though cardboard is also pretty floppy, so the mechanism here is probably different (mostly the puck guard keeping fingers out)
Like a cast saw or an electric toothbrush.