Even if they did buy all of these items from Unreal Engine Marketplace, I find it hard to believe they would use demo renderings for their promotional materials.
If they could pass off another project's whitepaper as their own, then these photos were very likely stolen as well, because those assets are still for sale on the Unreal Engine Marketplace, implying that no one has ever purchased them. Is it possible that photos aren't taken down after they've been sold?
There's a lot of NTF and video game nonsense out there these days, and this is just one of them.