I suppose the ending finally affirmed something initially hinted at in the Soul Society arc, and again in "Deicide":
As correctly guessed by Byakuya early on, Rukia only really cared about Ichigo to such an extent because he looked just like Kaien, and that was proven later on when Rukia's mind imposed the image of Kaien onto Ichigo when he first met her again in the Soul Society.
In other words, Rukia could have never truly "loved" Ichigo, if all she ever did was subconsciously relate and compare Ichigo to Kaien. After all, wasn't her guilt over Kaien the reason why the Hogyoku sent all her powers to Ichigo instead of just half? And it just so happens that Ichigo looks just like Kaien? And Aizen just happened to know that one of his Hollows killed Kaien, whom Rukia was a subordinate under?