That passage just irked me.
Just one? I could write a book length response to all the things that irked me about that essay. I've seldom seen such a dense field of flame bait.
I can roleplay a social character, but only so far. It's not my skill as a roleplayer that's lacking, but my social skills in general. Hey, unsurprisingly, I'm a nerd. I also not entirely neurotypical and have some problems with social cues. I find being around people tiring. Exhausting. I can't always be social, I can't always give my A-game. And it's nice for the mechanics to be able to help me out when I'm just not able.
While I don't agree with you that social and physical skills within a game can ever be handled in the same way, because the mind of the player is present in the shared imaginary space in a way his body is not, I otherwise sympathize with what you are saying here.
The compromise that has always worked for me is to insist that the player provide the content of his social propositions in character, but to judge the response to that content based on a combination of the fictional positioning and the social game mechanics.
So, you stutter out whatever you say, and once I get the gist of it and have enough of an idea how the NPC would respond to your content, then I'll judge what sort of social interaction you are making - deception, reasoning, intimidation, etc. - and ask for an appropriate skill check. The difficulty of the skill check will be slightly modified by the context and suitability of the content. For example, a man who cares for his children will have the check modified if your content refers to his relationship with his children, and the outcome of the proposition whether success or failure will depend on the combination of your content and the NPC's character.
If your character tends to have high social skills, however awkward your personal social skills are, in game there will be a tendency for people to like, respect, and perhaps fear your character. Your stuttering, stammering, blushing, long windedness, shyness, and so forth doesn't get translated into the shared imaginary world unless it is suitable to the character. Conversely, no matter how charismatic you may be personally, if your character lacks the same traits, then everything you say in character will tend to be seen in the worst possible light in the shared imaginary space.
And this happens precisely because that's what the rules say will happen. Now, it still can be that you'll fail repeatedly in social scenarios because you deliver IC all sorts of inappropriate content - japes when its not suited, threats that are ill-advised, lies when the truth would serve you better, and so forth. But that's the same as choosing to open the wrong doors or failing to adopt the right tactics in a battle. And, regardless, the rules will tend to mitigate your bad decisions in the same way that a fighter of extraordinary ability doesn't need to be quite as much of a tactician.
However, I always insist on making a person speak IC, both because it makes for a more enjoyable game, and because I find that its good practice and tends to increase the player's 'skill points'.