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/
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/