See the foliage. Notice there are proper shadings on the trees & grass, dark & bright areas that react to the light source. Then look at the flat foliages in the final product.Notice that there is next to no light & dark area on them that react to the lightsource. The only thing they have are casted shadow, & thats about it.
Notice also the bright rim light at Gerald left shouderpad & hair in the picture you posted, then see the basic & guadual shading on Gerald clothing & hair in the final game, on a supposely bright day.
Have no doubt about it, lighting has been downgarde by a level or 2.
Trailer still
Final Product