I think this sentence says a lot. You, as well as innerdude above(and Alexander, if I'm reading him right) seem to be going by a definition for roleplaying that only accepts the Actor Stance as roleplaying, and puts Author and Director Stance outside it. It's this rejection of the other two stances that leads to the attitude in the article that gets my hackles up.
He called them "nothing more than mechanical artifacts" only if they're dissociated -that is, they have no place within the game world. So, again, if they cannot be learned, explored, or observed in-game, than they are "nothing more than mechanical artifacts." He does not, as you seem to imply, say that all mechanics are "nothing more than mechanical artifacts".
The more I think I about it, I suspect the essay (or its implications) is not a rejection of any one stance per se, and I agree with Jameson's statement.
To take a very extreme example (because I need to find something that we can all agree upon!), your party has been plagued by the most obnoxious despicable annoying Kobold ever. You hatch a plan and spend days and days setting up a trap. Beyond all expectations, you actually manage to capture him in a force barred cage and it shrinks so that he's immobilized. You then toss the cage into a see-through force vat full of hellfire hot lava. The torrent of lava spews thru the bar cages, not affecting the force cage, but devastating everything inside it. Yet the kobold is inexplicably alive.
Assume this LoonyTunes Uberkobold is a standard kobold with 300 hit points. The lava does 100 hit points of damage with a save for half damage. Arguably, though, the mechanic of making a saving throw to take half damage is disassociated from the fiction of being immobilized, and the mechanic of hit points is disassociated from the fiction of obliterating lava.
In Actor stance, the player AND PC blink in astonishment. They can't believe their own eyes. While the PC wrestles with things beyond understanding, it's easy for the player to fall out of immersion and start questioning the mechanics or plot device instead of taking the fiction for granted.
In non-Actor stance, the PC blinks in astonishment while you just try to flesh out the cause-and-effect. The kobold is actually a god, or he has magic shielding, or the kobold snuck in last night and purposefully set off the trap with a lifelike replica that is actually a construct with immunity to heat.
So what actually happened?
If a 300 hit point immobilized kobold survived the lava, then it doesn't matter if you're in Actor stance or not. The mechanics are quite disassociated from the fiction.
If the kobold was a fake construct (and nobody made a spot check) with immunity to fire, then that mechanics is NOT disassociated from the fiction, and perhaps you'd be more likely to connect the dots in non-Actor stance.
However, whether you've picked Actor stance or not, (dis)association is still about matching up what mechanic to what fiction. The only difference is that each stance offers a different spectrum of fictional match-ups to any one mechanic.
With all its flaws as a single unlikely anectode, it can only go so far as to theoretically suggest that taking a non-Actor stance may provide more fictional options but does not make your game immune from potential disassociation. (Nor does it help much all those many people who do want to play in Actor stance.)
The counter argument is that this an extreme example, and in my game, I can always find a way to associate the mechanic to the fiction. The counter-counter argument is that I thought a lot of people have been discussing disassociation at the theoretical level and not actual average gameplay, plus I have to eat lunch now--