We had a similar theory here a few days ago, and I’ll say about the same thing here as I said there:
If true, don’t care.
I mean… we don’t really know anything about the First Ones, except that they build the Zereths. Revealing that someone or something is one of them doesn’t hold any meaning for me right now. “Aman’thul actually isn’t a Titan, he is a super powerful being of Order that wants to establish order in the cosmos” is about as much of a revelation as “Nozdormu has his aspect powers back, so he can now travel in time, just as he did last week, but more!”. And no “that mysterious being inside of Azeroth is actually of a kind of other mysterious beings that we know nothing about”, doesn’t help in getting me interested, either. It’s like saying “Her power level is over 9000!!!” without even establishing power levels.