It was also just a good season finale in general. The worst interns are taken care of (Murphy off on her life, Shane to Switzerland). April makes good with the world and Mama Avery. And there's conflict to deal with come September: a new character was introduced and it's Ellis Grey and Webber's child.
April and Jackson feel ambivalent about their baby; Webber wants Yang to repeal the Harper Avery and cranky about the talent drain and the foundation. Jo is totally overworked. Bailey put the deactivated HIV cells in the bubble boy without parental consent. Derek has Amy in town and they are performing surgery on conjoined twins, like two best friends we know are about to be torn apart.
Webber goes to Boston to see Catherine for a romantic rendezvous, but it also ends up being a deposition as to why Yang lost. What's the Avery Foundation's beef? Turns out it's that she works at a hospital co-owned by the foundation. And now we know why Yang will be leaving. She can't fulfill her dream where she is.