You are exactly right. You can model things that way. And it works. Why can he push through? Well, he's still got some hit points left. That's because hit points work on a linear time frame. If he's still moving, he's got hp left obviously.
4e just doesn't work that way. Not that it's a better way of doing it, but, rather, a different way of approaching the issue.
People keep trying to apply an approach that 4e just doesn't support and then complain that 4e doesn't do what they want. In 4e, a wound is never, ever a fixed narrative point until AFTER everything is complete. That's the whole point of it being abstract and a narrative based concept. Everyone at the table has the opportunity to add or subtract from the narrative at every point in time, up to and including ret-conning narratives.
The orc attacks you and does X damage. That's all that's known. Until the combat is over anyway, and THEN, and only then, can you pin down the narrative. Granted, most of the time, the narrative does follow in a fairly linear fashion, but, that's simply because none of the players have changed the narrative as its being played out.
Your character takes a butt load of damage. Combat ends and he spends his healing surges. Now he's back at full hit points minus those healing surges. What happened to his gaping wound?
It never happened. There was no gaping wound. Even when the character fell down and was possibly dying, there was no gaping wound. Why not? Because the Warlord yelled at him to get back up and it worked. If he had a sucking chest wound, no amount of yelling would have made him stand up. But it worked, therefore there was no sucking chest wound. That blow that looked so bad was just stopped by the Mithril Armor and the character had the wind knocked out of him.
However, had the warlord not yelled at the PC, and the PC then failed his three death saves, then that wound would obviously have been a sucking chest wound, because, well, no one dies of having the wind knocked out of them.
Now, I can totally see why people might not like this way of doing it. I get that. But, the argument about "realism" just doesn't wash. It's perfectly realistic, but, you just have to apply the narrative after the resolution of the event, not as it occurs.