While I see where you're coming from, and the position you're standing on, and don't entirely disagree with that perspective from that perspective, there's still the issue of subjectivity.
How opaque is that fourth wall?
The significance of the fourth wall carries quite a bit of weight in the verisimilitude department.
Certainly, dolls, puppets, animated cartoon characters, computer game NPCs, and the entire species of simulacrum are designed with empathy-engaging anthropomorphism at their core to promote interaction. The Furby toys, Tomagochi, and other similar toys are, for instance, designed to exploit the Benjamin Franklin effect. https://en.wikipedia.org/wiki/Ben_Franklin_effect
By doing favors, caring for these needy toys, it creates a reverse dependency. The same principle also underlies many unhealthy codependent relationships.
In computer security, information technology, and old school grifter circles, this is one of the methodologies for a social exploit, or social engineering.
Some of this was part of the unspoken between-the-lines and underlying dialogue of the recent film titled Ex Machina.
What works on some, however, may not work for all. This is the fourth wall, and there's those with more discriminating and exacting standards when it comes to allowing that suspension of disbelief to work its magic.
Fallout 4 is certainly sophisticated, and with the addition of protagonist voice acting adds a stronger level of engagement.
The whole question, or problem with developing virtual romantic relationships, however, comes down to that subjectivity.
I see it as a game, and am not going to invest much by way of emotional investment with characters who are there to serve me.
Sure, if the NPCs are sophisticated enough to take days off, quit your service for their own designs, all without your consent, that would be a nice level of realism in the respect that consciousness is often a measure of non-compliance; the ability for an ego to say "no"in spite of reasonable demands or requests with logical reason to back up non-compliance, if only it's a 3 year old child saying "No" because they just don't "want".
I still see Fallout 4 as a "simple" game.
I can turn it off. I can mod it. I can do whatever I desire within the restraints of the game universe to any and every character, and the only consequences are those I seek out.
So long as I maintain that perception, or until such time as that perception can be reasonably broken, I'm not going to have much by way of moral conundrum over simulating a virtual relationship, just as I won't have much of a problem making a character's head explode.
Until it reaches out into the real world and starts effecting physical reality, I'm not going to have much of an issue with or attach any weight to any virtual relationships.
Others, however, might. That's the subjectivity of it.
As to strong general artificial intelligence that could potentially be "conscious", that's another issue considering we've yet to formulate a robust enough model to give proper attribution and provenance to what consciousness actually is.
Whatever the case, I look forward to strong autonomous AI.
For now, however, the opacity of the fourth wall in Fallout 4 isn't sufficiently sophisticated enough such to sway my objectivity, and subjective perception.