I had thought that shading would be an issue as well, but given the way the room and other lights are arranged, even the lower branches are getting ample light. This would have to be something each grower would have to determine based on their setup.
As long as the rest of the plant is getting light, letting it grow to the glass is no more or less artificial and imitative of mother nature than the act of growing a plant under lights.

The plant doesn't know if it's 10" or 1" away from the bulb. It knows how much heat it has and now many lumens etc.