The reference book here is a collection of dialogs made by Cicero where he argues that there are two types of oratory: the short, "elegant", straight to the point one and the profuse, "appealing", heart touching one. Cicero himself says (in that book) he is in favor the latter. The book is not about nuance, but rather discourse style. In his (Cicero's) view, the better oratory style is the one that touches the audience as opposed to carefully chosen words. Based on the book, IMO, Cicero is more focused on arguing in favor of passionate speeches than nuance per se.

PS. I believe the quotes used are a bit misleading because they are used as counterexamples in the original text.