McArdellje
An occlusion strength of 0 should look identical to a material without an occlusion map
but in this case it looks identical to an avatar with a pure black occlusion map
this is because in the shader the occlusion map is multiplied by the occlusion strength when instead it should be
lerp(1.0, occlusion_map, occlusion_strength)
the issue can be seen in the first attached gif as well as the comparisons with no occlusion map and a pure black occlusion map
the second attached gif shows how this should look by using the unity built in standard shader