No. You add Artes Liberales and Philosophiae because you are casting a Ritual, and you are not deviating from "standard voice and gestures" (in fact, you cannot): you are using the (firm) voice and (bold) gestures standard for Ritual casting, which may well be different from the voice and gestures standard for Spontaneous and Formulaic spellcasting but follow the same mechanics (e.g. in terms of how far R:Voice reaches).
You do recognize that quote comes from inside "Non-Ritual Spells" and immediately following "non-ritual magic," right? So the book has explicitly identified that it is not discussing ritual spells there. So that statement is describing formulaic and spontaneous spells, but not ritual spells.
There's a subtle fallacy in this argument. The discussion as a whole may be about non-Ritual spellcasting, but the individual sentence may well be about spells in general, stating a "standard" to which all generally adhere, but from which Spontaneous and Formulaic ones can deviate.