Board Thread:General Discussion/@comment-3244769-20160228202309/@comment-29325824-20180803103102

Vandiir wrote: A shinigami has to train for ten years after achieving bankai to master it, before being able to effectively use it in combat. She most likely attained it before or during the series and mastered it while with the Royal Guard. Highly unlikely she just got it as a result of training with them. If so, every other lieutenant might as well have gone to the palace too for a free bankai.

No, I highly doubt Rukia had achieved Bankai before. Even if she hadn't mastered it, just attaining it is enough to boost her power immensely. I go with the idea that Ichibe outright told her what her Bankai is, allowing her to instantly achieve it.

As for why not all Shinigami get that? Simple, it's not Ichibe's job to give everyone a free Bankai. Normally Shinigami do have to work for it. Rukia and Renji were just exceptions because of the dire situation. That and they were friends of Ichigo and Ichibe probably knew that they could be trusted with the power, as opposed to some other Shinigami.