I think it’s about knowing that self is not multiplicity. But the oneness that is talked that one has to remove attachment towards when reaching it.
But removing attachment to it why? Isnt it because it cause the illusion of multiplicity?
Although you see it correctly as unity. You still have to let it go to let go of multiplicity. It’s like a giving someone a hand shake. Than letting it go. To be yourself. That is free to move in any direction.
Imagine a person hand shaking too long. You can’t wait to be free.
In the same way, householder, a disciple of the noble ones considers this point: ‘The Blessed One has compared sensuality to a chain of bones, of much stress, much despair, & greater drawbacks.’ Seeing this with right discernment, as it actually is, then avoiding the equanimity coming from multiplicity, dependent on multiplicity, he develops the equanimity coming from singleness, dependent on singleness, where sustenance/clinging for the baits of the world ceases without trace.
— [MN 54]