On an aside. I actually wonder if this variation in responses might be an evolutionary thing. Even before our more admin heavy times, death was - in a purely practical sense - a complicated thing to deal with. Maybe the cold fish are a necessary part of the mix - dealing with the practicalities while everyone else gets to grieve. This is me, up and dressed. Not that I'm a cold fish as such - it's just that I tend to be what you might describe as emotionally neutral in the first instance, the grief not kicking in until much later (often months after the fact). And guess who gets to do the bulk of the organisational stuff?
Another thing. I think we tend to view the McCanns as the parents of a dead child, rather than a missing one - and I suspect the processes involved are a potentially very different kind of complicated in the case of the long term missing, when compared to the known dead. I've heard of cases where those close to a missing individual actually resist the normal processes of grief, because the abandonment of hope feels like a betrayal of their loved one. Or where, if they do feel grief, it's accompanied by a terrible sense of guilt - for the same reasons. It's got to be one of the most awful things for a human being to deal with.