As an erstwhile teacher of Latin myself, one who do indeed love that language, I must say I never approved of its being a required subject anywhere. It should always be an elective course. That said, I think a study of Latin, with its carefully analysed and described grammar, and curious but for the most part reasonable methods of developing vocabulary, has over the centuries aided missionaries in making their own disciplined study of newly encountered non-European languages, and then in passing along a formal description of those languages to others.

There are different ways of learning a foreign language, and different ways of measuring mastery. Fr. Rother's achievement was remarkable; my guess is he had a talent for picking up the conversational habits of the native-speakers, but perhaps was less interested in elaborating a formal grammar.

BTW, conversational Latin is not taught among most classicists. And I wonder at the quality of the Latin spoken in seminaries.