A seedling is the same in that, like the embryo, and the fetus, it is a new life. I wouldn't call a seedling an apple tree. But then again, I wouldn't call a newborn a teenager. They're in different stages of development but all very much alive.
I think that if someone showed up with a zygote from my dog, I'd want to know where they got it, and why and how they kept it alive. It wouldn't replace my dog. But if it were allowed to grow into a puppy and be born, I could have that part of him.
I have cats and birds though so it's a moot point I guess..