I don't know, Shaun is a bit of a crazy weirdo with unlimited resources running a weird social experiment.

He created a Synth version of himself to play out his lost childhood, why not a Synth version of a parent who loves him?

I think the best thing about that line is that the player is left to make their own conclusions. If you like the idea, the Survivor is a synth, if you don't, they aren't.