I think you are talking about Sanctus by Libera, which is based on Canon by Pachelbel.
Many Korean TV programs have been using the introduction part of this song to make the scene holy in fun way. 'Ah' is not a word but after that part, there are some lyrics. https://music.naver.com/lyric/index.nhn?trackId=5204267
It's most likely that most Korean viewers feel repulsive hearing vulgar words.
From the society where the modesty is the greatest virtue, spitting harsh words are immediate turn-off to mainstream viewers.
This environment affects both script writing and subtitles.
(subtitles from western movies are also likely toned down)