Is this a plothole? Question about the Endless

[Nitelancer]

If they could pick apart the contents of memory and souls, then there wouldn't be anything stopping them from manufacturing their own without needing to commit multi-genocide across the reflections.

I think the endless are supposed to be based on the happiest memories of the person or the happiest version of themselves. If that’s true, then they must be able to distinguish between the good and bad memories contained in the aether.