It's been sometimes observed that statistically, in a sentence, new information to the listener tends to come later than old information (but this can be easily contested: things can be moved to the beginning and be given emphasis in many languages: e.g. English "I didn't see your brother there, it was your sister who was there!"). I suppose D'Ooge may be equating being new to the listener with being "important"?
ēlūcet mâiōrem habēre vim ad discenda ista līberam cūriōsitātem quam meticulōsam necessitātem
It is clear that a free curiosity has a greater force in order to learn these things [languages] than a necessity based on fear. (St. Augustine, Cōnfessiōnēs I.14)