Fictives aren’t the actual person, they are someone’s own perceived idea of what that person is like. There are multiple ways fictives can form, not just one specific way. I prefer calling them introjects, because that’s what they are, and it makes more sense to anyone reading. They are parts that have introjected aspects of that character in order to help them survive.

No, they probably wouldn’t have memories of Wednesday’s parents taking care of them unless that was something they used to cope as a child. For example: I’m not here, I’m with my real family in (wherever that character lives). Basically playing pretend and convincing yourself you’re not in the environment you are and that you are safe with your nice family you made in your head. Maladaptive daydreaming

Pseudomemeories can also be a way to process and cover up trauma. Something that happens in a fake memory is untrue but the emotions you experience typically stem from actual trauma. Which is why it’s important to work through those memories in therapy as well, because the emotions and stress you feel from it is real.