I fully understand the perspective you hold about non-duality vs duality and I have in fact experienced this as well as I am no stranger to metaphysical experiences of many different kinds .
However when you break it down and try to observe the topic without self opinion and expectations and just look as it what you will see is that non-duality is a figment of the imagination/ assumption that one make in there mind in order to understand the situation and that is it nothing more nothing less. It is an assumption that this is all 1 coin because if it is all 1 coin then we can get a grasp of it mentality and feel as if we in some kind of way understand it and this is how the human mind works.
But the fact is that we are in duality and only are capable of experiencing that which is within duality as well.

and to even contemplate what true non-duality is like is impossible because you would be using the mental tools that only work in duality and are incompatible of working on anything outside of duality so then if one experiences so called non-duality it is an illusion of the Mind and it's still part of duality.