I suppose that it was only matter of time before Facebook Stories Unite. But I must admit I do not see reason why there were more versions. Facebook, Messenger and Instagram are three services which operates on the same base.
And people who communicate on Messenger follow themselves on Instagram and vice versa. However only now there come unification. It means that when you post your Facebook Story on Facebook only or on Messenger too.
As well part of this is possibility to send Stories from Instagram to Facebook. There are still some flaws and mistakes. But in no time, there will be only one stories I am sure of it. Are you excited about this?