Disable ambient occlusion makes model lost smooth lighting

When disable ambientocclusion in block models, this block model will also lost smooth lighting, make it just looks like smooth lighting off.

Provided image is comparation using a custom resource pack which just add "ambientocclusion":false into spruce trapdoor models, and place a redstone torch nearby, under large area covered by blocks to make sure no other block or sky lighting, and let result more obvious.

We can see the lighting on left spruce trapdoors is different, and when ambient occlusion is disabled, lighting on those trapdoors is no longer smooth.

We expect disable ambient occlusion only disable ambient occlusion, but not also smooth lighting.