I think All Hail the King did what it wanted to without bending over backwards to appease people who were mad at IM3's twist - the real Mandarin always had the potential to exist, and I'm pretty sure IM3 directly referenced that. The short was just much more explicit about it.
Even though Drew Pearce said this could be a doorway to IM4 or 5, I sure hope it isn't, because I don't want shitty racist caricature Mandarin to be a thing in IM4 unless he gets brutally murdered in the opening ten minutes.