You can see that even each blob is fairly specialized already. I wouldn't compare that development to evolution. Just to the fact that cells specialize similarly at first, and then genes contain the instructions for actual development from there.
It's just fun to compare it to evolution in some ways, with similarities then evolving into traits for each individual. It just shows how similar we are to having back bones, skin, teeth, organs in systems, and even the same systems from digestive to respiratory. We aren't all that different, but at the same time very different at the end result from very small differences at the genetic level.
I hope this makes sense. If anyone can explain this all better, please do.
Otherwise, just look up a bit yourself about notochord development in evolution compared to spinal cord development in embryos. Then animals who get vertebra compared to those who only have a notochord still.
You don't get vertebrae forming in an embryo until you have the spinal cord forming.
It's like building anything. You have to start with the basics and then add finishing touches. Having a body of the car made before the engine may result in the engine not fitting the body.
Evolution just kinda follows that too. Why develope vertebra if you don't even have a notochord? How would you get spinal chords evolving if notochords don't show up first?