alt Hacker NewsYou could have an alternative explanation: large animals invest lots of food energy in their offspring, and so the slimmest chance that a calf might not be dead is worth lots of effort. Say one in a thousand actually revive.
Here's an article about orcas: https://www.bbc.co.uk/news/science-environment-64559047
It seems that an orca invests so much in a son that it's like an all-or-nothing one way ticket to pass her genes on. (She might get second try later, but the probability is much lower.)
You might also argue that although there may be a non-emotional argument for why grieving could be beneficial, it’s possible or even likely that evolution encoded this instinct in something like emotions. Just how evolution encoded the tendency to care for one’s family and community in emotions for humans.