Stan Lee isn't an unreliable narrator. He's a dishonest narrator.
Per Abraham Riesman, "Stan Lee lied about little things, he lied about big things, he lied about strange things, and there's one massive, very consequential thing he may very well have lied about. If he did lie about that last thing—and there's substantial reason to believe he did—it completely changes his legacy."
Stan Lee never truly cared about the narrative elements of any of the comics he worked on (mostly because he was largely not involved with it).
Nope. Steve Ditko when he was alive, time and time again confirmed that he intended Norman Osborn to be the Green Goblin:
"Now digest this: I knew from Day One, from the first GG story, who the GG would be. I absolutely knew because I planted him in J. Jonah Jameson’s businessman's club, it was where JJJ and the GG could be seen together. I planted them together in other stories where the GG would not appear in costume, action. I wanted JJJ’s and the GG’s lives to mix for later story drama involving more than just the two characters. I planted the GG’s son (same distinctive hair style) in the college issues for more dramatic involvement and storyline consequences. So how could there be any doubt, dispute, about who the GG had to turn out to be when unmasked?"
I mean think about it, if Ditko who was never shy talking about and complaining about Stan Lee or setting the record straight and was vocal about disagreements had a big stink about Norman being Green Goblin don't you think he would shout it from the rooftops. Instead he consistently denied this claim.
Steve Ditko had plotting credit from ASM#25 onwards, which for those keeping track includes the lead-up to the Crime Master 2-Parter (ASM#26-27) which had Norman Osborn's first named appearance in comics.
Ditko designed the characters and he had Norman Osborn with his distinct Cornrow hairstyle. His final issues presented Norman far more unsympathetically than how Lee-Romita depicted him.
And there's also visual foreshadowing. Go to ASM#27, take a look at this silhouette of the man behind the goblin costume and compare the silhouette of the hair-style to Norman introduced in the same comic and consider that in Ditko's run every character had a distinct unique hairstyle for the most part.
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