although a valid translation, it's a narrow sense of the word, and just reads funny to me to say it like that. Same with how the catechism uses "stuprum".

For example, seneca the elder writes (in reference to vestals): "incesta est etiam sine stupro quae cupit stuprum"

Using the catechism's restrictive definitions of "incest" and "rape" for "incestum" and "stuprum", we end up with nonsense: "she who desires rape is incestuous even without rape", while the correct sense is indeed "she who desires illicit sexual activity is unchaste even without illicit sexual activity".

so, yeah, to my eyes, it just reads funny -- it makes categorically broad terms into a narrowly defined term, so when reading it, it just seems awkward.