Oh my goodness, that is completely ridiculous. I would never claim to have good Latin, but my Latin is definitely good enough to know that Patrick is not calling on Helios there! The whole episode also touches on one my bugbears as a former Celticist — this persistent belief among certain scholars that Ireland was some kind of fantasy pagan paradise, and that Irish (vernacular and/or Latin) texts written or transcribed in ecclesiastical contexts, by Christian clerics, often well into the twelfth century somehow are filled with accurate contemporary details about surviving pagan belief and practice. It makes me grind my teeth with frustration.

In my experience, there are numerous medievalists who have limited language skills — not just in Latin, but also in the vernacular languages they work with, and in modern non-English languages. For example, as a Celticist it's useful to have a working knowledge of Modern Irish and/or Modern Welsh, and German and French — otherwise it limits you in terms of the scholarship you're able to read. My former department (I'm not an academic any more) really emphasises language proficiency and makes it very easy for its students to gain high levels of fluency in all relevant languages, but not all medieval studies programmes do so.