That's actually one of his posts I find the most disappointing, narrow, and flawed. I find it so because he started with the premise and then went looking for the support, and so engages in special pleading, cherry picking, and false dichotomies to support it. Elsewise he'd have had to skewer hitpoints, saving throws, armor class and a host of other things that pre and post date 4e.
At the end he does admit to things like character creation and advancement being disassociative..
Does this mean that dissociated mechanics simply have no place in a roleplaying game?
Not exactly.
First, dissociated mechanics have always been part of roleplaying games. For example, character generation is almost always dissociated and that’s also true for virtually all character advancement systems, too. It’s also true for a lot of the mechanics that GMs use. (In other words, dissociated mechanics are frequently used – and accepted – in the parts of the game that aren’t about roleplaying your character.)
Second, people often have reasons for playing and enjoying roleplaying games which have nothing to do with playing a role: They might be playing for tactical challenges or to tell a great story or to vicariously enjoy their character doing awesome things. Mechanics that let those players scratch their itches can be great for them, even if it means they have to temporarily stop roleplaying in order to use them. Games don’t need to be rigid in their focus.
An extreme example of this are people who play roleplaying games as storytelling games: Their primary interest isn’t roleplaying at all; it’s the telling of a story. (In my experience, these players are often the ones who are most confused by other people having an extreme dislike for dissociated mechanics. After all, dissociated mechanics don’t interfere with their creative agenda at all. For a lengthier discussion of this issue, check out “Roleplaying Games vs. Storytelling Games”.)
In short, this essay should not be seen as an inherent vilification of dissociated mechanics. But I do think it important for game designers to understand what they’re giving up when they use dissociated mechanics; and to make sure that what they’re gaining in return is worth the price they’re paying.
The hitpoints are certainly played disassociatively by a lot of people who claim to not like those mechanics. (Down to 5 hp you'll charge the monster who does 2d6 because you won't get to -10 and die, but down to 1 or 2 hp you won't.) But is AC usually played disassociatively? Or do the characters just recognize that certain things make one harder to hit and react accordingly?