The old videos were all about the splatter quantities and not the qualities.
The old videos had very crude zombies, but as you can see from more recent posts,
the graphic qualities are always improving.

I develop the same way myself.
Design the level with blocks and spheres, get the movements right, then upgrade the models,
which Ive been working on elsewhere.
Improve the movements, modify the models to match if required.

I see the same development "style" in this thread.
Crude models and levels, get movement and splatter close.
Add real models, fine-tune movement and splatter.
Rinse and repeat...