Pretty much every complaint about 4e boils down to "These rules don't model a world I personally find plausible." Okay, point taken, but they don't try to.
If you work from the mechanics that describe how things happen, and come up with interpretations and explanations that make you and your group happy, you're set. Yeah, it's some extra imaginative work the books leave to you, but that's how they did it.
The reason damage and healing work the way they do is a pacing mechanic, pure and simple. It's up to the people at the table to decide how that is represented in the fictional game world, and that'll probably differ from table to table. There are some definate guidelines (such as the indication that if someone is bloodied that indicates actual injury, whereas HP loss above bloodied might just be fatigue or morale), but they're pretty flexible. The whole game pretty much works this way -- flavor text for powers, for instance, gives an example of how you might describe the power use in game, but it's not a "must".
If that's someone's general complaint with D&D, I don't think it's really necessary to pick out one particular way in which the rules do it, because they do it all over the place. I'm not saying people don't have the right to complain about the little examples that particularly bug them, but it's sort of small potatoes compared to the general large difference in how you picture mechanics translating to in-fiction "reality" in this edition compared to some of the old ones.