That's not really what we're talking about, though. It's a poor analogy.
Nobody's ever seen a healing surge. Most everyone has seen cats and dogs.
It's a game mechanic that takes place in an imaginary space, not a real object. I don't know that there's a need for a mechanic to have the same narrative justification each time it occurs.
I mean, we've already talked to death about hit points, and how HP can mean different things at different times. We could talk about action points, and how they could be narratively justified in different ways - maybe a surge of adrenaline, maybe a critical opening, maybe perfect timing, and so on. We could talk about how a barbarian's rage could be him getting really angry like the Hulk, or just him going into a frenzy of battle. Or how some Fighters are militia men, others are knights, and others are mercenaries.
This isn't new, IMHO. There's no 1:1 correspondence between mechanics and narration, and there hasn't ever been that I can see.
-O