We don"t see a lot of things in the video , and the camera is too far and don't ove to show the normal and specular effects, a little useless ? What make me sad , is that other engines propose complete lightening and shaders integration, and some propose Deferred shading alreay Not only Unity 3D , some low cost engines like LeadWerks engine propose also that deferred shading.
So 3DGS makes me a bit sad in that areas. That's like lightmaps import on models that is a hell on workflow compared to some other engines.