Is ByBlock a viable answer to plastic pollution

Anybody here familiar with this stuff? It looks like a great idea - especially when you consider that the built environment is going to expand tremendously in the next couple of decades and both concrete and lumber have high ecological costs. Living in the fire ravaged west, my main concern is how it stands up to a forest fire - their FAQ simply says it will require the application of a fire retardant. But burnt plastic releases all kinds of toxins that lumber doesn’t contain.

I also wonder if they could modify the Blocker to make different shapes…