Why Glb Model Not affected by SkyBox Pbr Material?

ex. https://playground.babylonjs.com/#UU7RQ#2752
glb model is black,not affect by skybox material,
but in sand,when i drag glb into,its affect by skybox(i check there is no light in scene)

glb00001.zip (2.8 MB)

The reason is that skybox itself is not a light source. It has reflection texture, though.
To use .env files with PBR you need to define scene.environmentTexture.
Example - https://playground.babylonjs.com/#UU7RQ#2754