This corpus is not a well thought selection of presentations that achieve a predefined set of communicative/argumentative goals. On the contrary, it was intended to be the starting point for coming up with such a set. The samples in the corpus were selected because they appear to be interesing in an intuitive way, not because they illustrate a particular aspect of a pre-existing theory.
Very rarely you will find comments like "this presentation is not effective in making such a point, in presenting such and argument, etc." and the corresponding advice "such point should be made in this way....". Again, building the corpus is only a first step, let's call it a descriptive step in building a theory of textual-graphical arguments. A prescriptive step will follow but in the corpus you can only find feeble hints to that.