Degree condition for maximum-length cycles in bipartite digraphs

Let $D$ be a bipartite digraph with colour classes $X$ and $Y$ such that $|X|=a\leq b=|Y|$. For vertices $u$ and $v$ in opposite colour classes with $uv\notin A(D)$, consider the degree condition

$$d^+(u)+d^-(v)>\frac{a+b+2}{2}.$$

Maximum-cycle degree conjecture. If this inequality holds whenever $u$ and $v$ lie in opposite colour classes and $uv\notin A(D)$, then $D$ contains an oriented cycle of length $2a$.

This is an Ore-type sufficient condition for a bipartite digraph to contain a cycle meeting every vertex of its smaller colour class. The source states that the conjecture is proved in the balanced case $a=b$, while the general case remains open.