I see where you are coming from, but I don't think I agree. The author doesn't make reference to physical or non-physical. He might be a physicalist, or he might not be, but in any case I think the point he makes is still valid.
You are right that the tangible real world is only temporary, but at the same time I feel the split is not fundamental.
In my experience often engaging with the real tangible world through perception, etc makes aspects of the inivisible world more clear in a way that abstract philosophy doesn't (which doesn't mean that can never yield clarity, of course).
Perception itself knows no split of the clarity of what is perceived and the endless space of perception itself. I don't think you can really have one without the other.
I don't really agree detachment from the tanigble world itself is the goal. If we take non-duality seriously, the tangible is just another aspect of being; why would we deny its importance by detaching from it.
I guess it's good to have the option of detachment and dissocation, and certainly transcendence, going beyond just the world is a worthwhile quest, but all of that doesn't really imply detachment as a goal in itself.
Like almost all spiritual traditions say, the deepest clarity and truth is found beyond just thinking. That's why I think it's so useful to go back to stillness, simpler thoughts, or less rationalist thinking again and again and root ourselves in something beyond the intellect.
It makes the intellect transparent to something beyond itself, so that we can get closer to wholeness.