[...] why present fake options in the first place?
Oh, I know the answer to this question: Because you fear that people will see your game as a Kinetic Novel.
This being said, you example is not a "fake choice", but an useless one. "Fake choices" exist, and are alas legion. They are choices that have no consequences whatever the option you'll pick. Not even a narrative consequences past the one line difference right after you made your choice.
The next problematic type of choice is what I call a blind choice. In a game I played recently the mc sneaks into a house to search for clues when suddenly he hears someone at the door. Now the game asked me whether I wanted to hide in the living room or in the bedroom and my choice determined how events would fold.
It's a "blind choice" only if the effective consequences change drastically. But it's not always what hide behind such choices, the change can be more narrative than effective.
Lets say that you're in school, half naked with a girl, and someone (a girl) enter the room. You've to choose where you'll hide, and depending of your choice, you'll be caught or not.
If the consequence of being caught is that the girl will join you, it's a "blind choice", because as player you've no possibility to know that it will happen. But if the consequence is the girl making fun of you time to time, it's a "narrative choice". It add more depth to the story, since the decision you make as player have an impact on its narration, but no unpredictable impact on the story itself.
How the hell am I supposed to know which choice is better or what each of the choices will do?
Unless the player takes pleasure in randomly following an unknown path, [...]
Isn't this a game ? Where is the pleasure to follow a fully predictable path and, by extension, why play if there's no pleasure ?
When you're facing the choice to defuse the bomb in Fallout 3, you aren't even sure that not doing it will blow up a town. You decide to do it, or not, dot. It's life, you only know the short term consequences, yet can't even be sure that they'll effectively happen.
There isn't a single game, and I'm not limiting to the adult scene, where you know what choice is better. At most you can only know what seem to be the better one. And if you save so often, it's because you're never fully sure that you were right.
Do you wish to attack the gangster or try to negotiate? Presenting a role or morality based choices helps the player to identify with the main character better and feel better connected to the game.
And what role, or morality is expressed by the choice to attack or negotiate with the gangster ?
I can be a highly moral guy that can't stand gangsters, thinking that their place is in hell, where I'll send him fast by attacking him. Like I can attack him because I'm a totally amoral person who want to take his place. It can also be due to the fact that I decided to be a totally irrational guy, or because I wanted to play a looser and expected to loose the fight. At the opposite, I can negotiate because I'm a coward, because I don't believe in violence, or because I want to works with him.
You aren't a bad guy because you choose to stand with the legion in Fallout New Vegas, nor a good guy because you decide to stand with the New Republic of California. You are just someone who have a different vision of the world and expect one way to do better goods than another.
What you are presenting here is way more "story choices" than "role choices". They are targeting the story way more than the MC. Choosing to attack of negotiate with the gangster will change how the story evolve, but as said above, do not define who the MC is. Or at least they do not define MC's role more than any other choices, including fake and blind ones ; the player decided to choose this or that, because he felt that it fit the MC as he is playing him, not just because he flipped a coin.
Effective "role choices" are something different and goes further than that. They imply a deep change in the game progression, not by changing the story, but by slowly limiting the choices offered to the player. The more you advance in the role you decided to play, the less you've options that goes outside of this role. They don't change the story, they enforce its coherence.
