Just adding this, which I should have included above. The last sentence is the one I'm trying to interpret.
https://www.law.cornell.edu/cfr/text/26/25.2518-1
"(b) Effect of a qualified disclaimer. If a person makes a qualified disclaimer as described in section 2518(b) and § 25.2518-2, for purposes of the Federal estate, gift, and generation-skipping transfer tax provisions, the disclaimed interest in property is treated as if it had never been transferred to the person making the qualified disclaimer. Instead, it is considered as passing directly from the transferor of the property to the person entitled to receive the property as a result of the disclaimer. Accordingly, a person making a qualified disclaimer is not treated as making a gift. Similarly, the value of a decedent's gross estate for purposes of the Federal estate tax does not include the value of property with respect to which the decedent, or the decedent's executor or administrator on behalf of the decedent, has made a qualified disclaimer. If the disclaimer is not a qualified disclaimer, for the purposes of the Federal estate, gift, and generation-skipping transfer tax provisions, the disclaimer is disregarded and the disclaimant is treated as having received the interest."
