What is kensho meant to be?

From my perusing of various sources, it seems like according to Rinzai, it's a lights on experience, according to Soto (Dogen), it not a part of Zen at all, and according to Chan it's just introspection of the nature of your thoughts (without any new sudden realization).

Are they just different traditions, or is there a way to reconcile these views? Did Rinzai masters just make it up, or did Dogen not get it, or what is going on?