The key word in the title is symbolic. In GeoGebra the CAS is not coupled to the drawing, and most of the computation on the drawings are numerical. In the link, everything you draw is symbolic and you get an algebraic expression in terms of the primitives you specify.

That's true, but you /can/ do exact geometric constructions that just use the CAS engine in GeoGebra eg https://www.geogebra.org/m/ZdhcBBpj

That's excellent, that is not nearly as difficult of syntax as I was expecting.