They NEVER say that their bond was based on their codependent-love for their brothers (in fact, all the way until this episode, there was NO codependency on Amara’s side)
THAT is fanon.
And sure, I am conviced that the writers didn’t plan for the conversation with the old lady to have more weight than Dean’s half-assed yellow crayon speech, but that was the end result (just like with the amazing world-saving toysoldier)
There is no explanation for the Bond, no real resolution to that storyline, and it was, in the end, as useless and baity as every single “hook” they give us about Dean.
With the extra cherry that it was creepy and non-conny as HELL.
(you REALLY want to tell me that the parallel is that Sam is willing to destroy the world in a tantrum if Dean doesn’t abandon all creation for him? UGH)