This explanation still leaves the mechanics fundamentally dissociated from the game world.
The problem with such mechanics, for me, is that they make roleplaying more difficult. When I'm roleplaying, I put myself in the shoes of my characters and try to make the same decisions they would make. The resolution of the course of action I decide upon will be done using mechanics my character has no awareness of -- but because there is a direct one-to-one mapping between those mechanics and the game world -- I don't become dissociated from my character.
If we choose to explain these mechanics in the way you suggest (and we pretty much have to, because (a) no explanation is given for them in the rulebooks and (b) no other explanation I've seen is even remotely viable), then you've suddenly introduced significant decision points for me -- as a player -- which have no relevance to the character at all. For the character, they're just taking advantage of an opportunity which has presented itself. But I, as a player, am deciding when that opportunity happens. My experience and the character's experience have been sundered.
That's my problem with dissociated mechanics: They distance me from my characer. And since roleplaying is the #1 reason that I, personally, play roleplaying games, that's a huge problem for me.
More generally, I find the explanation doesn't hold up very well to any kind of meaningful analysis. For example, let's take a look at a talented fighter who knows a Nifty Exploit. All he's waiting for is for an enemy to leave his back open so that he can use his Nifty Exploit...
On Day 1, our talented fighter fights a whole bunch of opponents who are significantly less talented and less skilled than him. He fights his way through five such encounters, dispatching dozens of opponents. During all of these fights against all of these opponents he finds only one opportunity to use his Nifty Exploit.
On Day 2, our talented fighter faces off against a single opponent who is actually much more skilled than he is. He's just as likely to find one (and only one!) opportunity to use his Nifty Exploit against this much more talented opponent as he was to find one (and only one!) opportunity to use it against a legion of lesser opponents.
How does that make any sense? It doesn't.
So now we try to excuse this by saying something like, "Well, see, against those lesser opponents the talented fighter never really felt the need to use his Nifty Exploit, so he didn't."
Of course now you've not only handed me a dissociated mechanic (which I don't like), you've been forced to justify it by also taking control of my own character away from me.
Describing these as "Voltron mechanics" or narrative mechanics has a bit more mileage to it. I'm certainly willing to accept the inherent disadvantages dissociated mechanics if I'm trading those off against the advantages of gaining meaningful narrative control. But, personally, I don't consider "when does Voltron pull out his Win the Battle Sword?" to be meaningful narrative control.
Or, to put it another way: Usually when I'm playing an RPG it's because I enjoy pretending to be somebody else (i.e. roleplaying). Sometimes people come along and say, "Hey, for this game I'm going to interfere with your ability to roleplay. But, in exchange, you'll get to be a co-author of the story." And that can be pretty cool, too, so I'm more than willing to do that.
But if you offer me that deal and then say, "And by 'co-author the story' I mean 'decide when your characters gets to use an Awesome Combat Move(TM)'." Then that's pretty lame and I'm not interested. Besides, I was doing all kinds of Awesome Combat Moves in 3rd Edition without anybody mucking up my roleplaying.