There are other tools you can safely use as a young kid and young kids can use knives etc they just need a lot of supervision and instruction. Hand saws are relatively safe compared to box cutters for example, they're unlikely to cut super deep but working with wood is a lot harder and more expensive. The cardboard hand tools mentioned elsewhere in the comments here are neat though they look like they work pretty well without having any sharp edges.

I agree, I'd do the Makedo style tools before this thing. But, I think the other part is this is an indoor activity with these tools. Handsaws would be outside for me (I don't want my house/furniture getting nicked during play).

The other part is, I simply don't want to heavily supervise their creative play. Everything kids do these days is planned and supervised, building a fort in your house shouldn't be.

Yeah do the hand tools and if they get into it in a big way this is a neat improvement, looks super easy to cut out complex shapes very quickly compared to the Makedo version.

I got some of their connectors in an Adabox I think a few years back and they were neat.