I think the purpose is so people can create their own variations of the available fonts, not to make animated text.

I really hope so. The web will be an unusable mess to me if fonts change size on scroll like in their demo page.

They're just demoing the parameters you can adjust to build a font. I assume they built the demo the way they did because it's more approachable for most than a long list of sliders with names that might not be meaningful to a lot of people.

That said, the way it works would certainly be off-putting to some. You may find their actual font builder app provides a better experience: https://app.prototypo.io/