However, here is even an excerpt from the medical sources: "The attachment of the embryo to the uterus is the process in which the fertilized egg is implanted into the uterine mucosa."
So yes, the fertilized cell is already an embryo. Open the wiki.

You just need to read further that the implant occurs on 6-10 days, and it is no longer a fertilized cell, but a blastocyst consisting of a large cell mass.
Read everything that is written, not just what is beneficial, readers of figs!