The crossover list-size conjecture for polar codes

Consider two polar codes $A$ and $B$ with the same code length $n$ and message length $k$. Let ${\rm FER_{SC}}(\cdot)$ and ${\rm FER_{ML}}(\cdot)$ denote their frame-error rates under successive-cancellation and maximum-likelihood decoding, respectively. Crossover list-size conjecture. If

$${\rm FER_{SC}}(A) < {\rm FER_{SC}}(B),\qquad {\rm FER_{ML}}(A) > {\rm FER_{ML}}(B),$$

then there is a list size $L^\prime$ such that code $A$ outperforms code $B$ for $L<L^\prime$, while code $B$ performs better for $L>L^\prime$ at high signal-to-noise ratio. The paper gives an example using $(128,64)$ codes.