There is no way that the sequence would have been a real one
Olympias outlived Alexander and Hephastion died just a few months before Alex's death.Therefore it's definitely a hallucination created by Aruna Irani's oracle.Killing off both Olympias and Hephastion and that too by Alexander himself would be too great a distortion and till now the CVs have stuck to history when it came to Alexander.
However that sequence was disturbing no doubt.Especially when they showed him killing the baby,Hephastion and Olympias.He worshipped his mother and Hephastion was a part of his soul.
I will agree with @PD on the matter that it symbolised Alexander letting go off his sentiments in one go.
But though he was ruthless he was not a monster.Till now the CVs have done a wonderful job with Alex's character by showing him as grey character.I hope they maintain it and don't turn him totally dark.