Let’s speculate…
Metatron was performing a spell in 9×18, “Metafiction”.
He was making sure, as he discusses with Gadreel at the end of the episode, that Heaven stayed securely closed.
And how did he perform that spell?
He ensured that Dean and Castiel did not reunite, but…
Metatron’s “Metafictional” Spell – The Ingredients (spoilers for SPN 9×18)
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