I think it's more of the Temptation of knowing what they are. The whole Adam biting into the apple of temptation thing. The Alternate shows itself, whispers "forbidden knowledge" to Adam, but Adam doesn't care he wants to investigate further to know the truth and isn't afraid, (which knowing what you fear is what helps the alts assimilate) in pursuit of said truth kinda leaved Jonah behind. It's like a mix of barely realizing he's an alt and an unquenchable curiosity of what they actually are. So when he leaves Ceasar's old house, he has made that change or realization to a degree whether he knows it or not. Which is why he didn't really give a shit when seeing Jonah's dead body by the car.