Yeah, if the baby (or anyone, really) had actually been dead for that long, then he would stay dead. What happens occasionally, though, is that the body’s functions are just slowed to such an extent that it’s hard for a doctor with nothing more than a stethoscope to tell that anything is still going on in the body. And so the person appears to be dead. It takes a much more careful examination to tell that the person is actually alive and breathing and has a (slowly and weakly) beating heart.
I expect that with babies, you have the added complication that the baby is sort of switching over from being connected to the mother’s system to having to fully turn on its own respiratory system. With an extremely premature baby, it might not do that so easily and so visibly.
Which is all part of the reason for the elaborate preparations and paperwork that comes before burial in modern times. It used to be that the local doctor (or “doctor”) would check the pulse, find none, and then the body might be thrown into a coffin and buried within half an hour or so. Which resulted in a number of people reviving and finding themselves buried, which I greatly suspect was not a fun thing.
There was a girl who looked after a few times years ago. When she was born, she had a tiny little tear in the outer muscle of her heart. The doctor who examined her noticed this, but decided all on his own—without consulting anybody else—that there was nothing that could be done about it. And so he didn’t tell anybody about it, not even the parents. When the parents were driving home from the hospital, the tear opened and the heart stopped working. The baby appeared dead, and in this case the heart really was no longer pumping blood at all. They rushed right back to the hospital and were able to get the blood circulating through the body again, but it had been something like ten minutes without blood getting to the brain. That ended up literally killing most of the parts of the brain that control motor functions. The baby was taken to a heart specialist who fixed the heart up again; it turned out to be a really simple procedure that they could easily have done and thus have prevented the whole mess in the first place. The girl grew up and had full mental capacity, but the only control she had over her body was that she could just barely move her eyes or her fingertips.
That was after just ten minutes of the heart not functioning. The baby in the article was nonresponsive for something like two and a half hours. If its heart had truly not been functioning, then there also would have been nothing left in the brain to function.