Implied gore is not enough, I guess.
Hmm. A flashback not many will care about. The most interesting thing was that this world's Mu traveled outside the array.
He isn't the same one from ages past in Daxia, right? Well, either case, not sure if it matters.
If he is the same person as that
Mu Yufeng, it could be a plot lore foretelling that we might see a path of the story that tells us how Mu has got a soul so powerful. There is no mention in the story, but it is likely to be true. If you think about it,
Mu Yufeng was a person that likes to read books about the dao. The
kid ( the one Immortal Godmother adopted ) was also a fragment of the Dao, just like this
Fengyu Piaoyao. I have no idea if
Mu Yufeng had looked like
Mu Siyun. The other two look similar though. Also, that
Fengyu Piaoyao also said something along the line of "We are the same person."