Etheric body must have puzzling properties. First, of course it better not knock the visible objects around. So for that purpose, it must not interact with the visible objects. However, it must also, follow the visible body. This, amongst other things, mean it must interact with visible objects!
But suppose we drop away the common 'spirit-matter' dilema? Then we can solve the above puzzle in elegant way. (When soul is incarnate in the 'seen' body, it is part of the 'seen' and not the 'unseen'). The 'spiritualness' need not be seen as a fixed artribute of a thing. Rather, it is what a thing can become or cease to be!
In the case of etheric body, the 'spiritualness' of the portion of body is corelated to its distance away from the seen body. Specifically, the farther away from the body, the more spiritual. At the point of contact with the seen body, it is fully 'physical'. Then the physical turns to spirit at the moment of leaving the body!