Agreed! Although I could pick out a few examples from the past the whole latin chanting thing is not actually common overall.
Also, just to tack another note onto your comment:
Serious as a tone can be reinforced in a variety of ways beyond just increasing the intensity of music. While it’s uncommon, some boss fights in games deliberately use a slower, less up-beat tone because it resonates thematically with what’s happening in the narrative. In the right circumstances, an unexpected choice like this can be much more powerful.