The point of concrete in construction projects is compressive strength to take heavy loads. This has a lot less. It's also unclear how well they'll hold up; you can already see bits of plastic flaking off as they place them in the video. Plastics degrade and shed micro plastics in the environment as they come in contact with the elements; it's very doubtful the structural integrity would hold.
Then there's the issue of safety. The plastic blocks have an even lower ignition point than wood, and a building on fire made out of these will releasing carcinogenic toxic vapours in the entire neighbourhood, also exposing firefighters to even more toxic fumes as part of their job. Plastic smoke destroys the lungs in a way that burning wood doesn't - you're screwed for life even if you escape the flames.
That's assuming making a whole building made out of petrochemicals and breathing that in all day long isn't going to give you novel forms of cancer already. Concrete blocks are also very cheap. I guarantee you these blocks are more expensive. It's not even good to send to third-world countries. For starters they're already under a larger burden of pollution (soil, air, microplastics) than westerners. All you'd be doing is putting them under an even larger burden.
But hey, buy our totally useless overpriced plastic block that will give you cancer to SAvE tHe pLanET. Or we could start using less single-use plastic in the first place so we don't need to create totally retarded dangerous products to justify their existence. It's no fluke the construction project they choose to showcase is a shed. Probably the only thing people will accept to build with it, if they have a brain.