The author reaches for such a broad definition of life that he ends up including unfertilized eggs. An unfertilized egg is as "integrated" of a "whole organism" as an fertilized egg. Thus a "human life" means a live egg than has been turned into a live human being by the process of fertilization.
embryonic individuals who have built the first form of the placenta they will occupy during pregnancy
The author seems intent on personifying cell specialization and other genetic processes. These exist throughout nature and in no way imply consciousness or survival instinct. They are simply predictable, predetermined actions.
When human form and human functions develop (I believe 8 weeks or so), then there is certainly an argument to be made for intentional actions by the individual. Otherwise I don't see how it is any different from what an unfertilized egg does, or for that matter an organ.
It was the intention of the author to purposely avoid defining these steps the embryonic human takes for survival as 'consciousness' in the sense that term is generally used. The term 'instinct' was also purposely avoided.
An unfertilized egg is a sub-unit cell of an organ. The conceptus, as it 'does' mitosis, fits the Dr. Condic assertion mentioned in essay one. The placenta is the first organ the newly conceived individual human builds. As to whom intended the placenta to be the essential organ for survival, I'll leave you to address that as you see fit.
The author is asserting that the placenta 'form' with its survival 'function', beginning as it does even before implantation, argues for the embryo at earliest age to be defined as a human being, a functioning integrated whole organism.