This is one of the reasons I like ASOIAF (Game of Thrones books), the author flat out says, these are the character's personal opinions/belief's/etc and they are not reliable narrator's as to what is fact or not.
I see a Ret-Con, when something was seen and is then later changed. The following is a ret-con:
In the Warcraft III and World of Warcraft game manuals (and in Sargeras and the Betrayal from the History of Warcraft), the eredar are described as being a demonic and evil race that had consumed their own world through arcane powers, and had already destroyed countless other worlds by the time Sargeras discovered them. It was not until after Sargeras destroyed them that he himself became corrupted, and the Burning Legion was born.
In The Burning Crusade, however, the Burning Legion had already begun under Sargeras' leadership when he encountered the eredar, who became corrupt through his influence. Furthermore, a faction of the eredar did not join the Burning Legion, instead became followers of the Holy Light, and renamed themselves Draenei.
Presumably, either another demonic race (such as the pit lords) take the place of the eredar in the role of corrupting Sargeras, or it is left completely up to the dreadlords. Blizzard has not released any official information on the matter.
Chris Metzen admitted the contradiction was a mistake in a forum post, but it has become the current story.
Taken from WoWWikki.
While I take something like, Garona's being said to be half orc and half human, to half orc/half Draenei as something from an unreliable narrator, even though it was changed, the writer's were able to play it off as if she was just mistaken for half human.