Becoming, and not fully a human. Does not mean it is not always a human
The acorns of a pin oak or a swamp oak, etc, ARE oaks, simply not at what we in our vanity and preoccupation with labeling would dub a tree. Since oak trees don't have dictionaries, the designations means nothing to them. An acorn, a sprout, a seedling, a sexually immature tree, a mature tree, a dying tree, a dead tree, a fallen tree, a rottng log. Only the last 3 of those 'stages' are different from the rest in terms of living creatures.
Like your pic of a horse egg, yes, it IS a horse, not a human. A living, developing horse. Kill it, it dies. That's the purpose of abortion, to kill.