It frustrates me when I read the example sentence in Japanese and English then the English translations often gives the literal or dictionary definition of the Japanese word in English. Which really throws me off.
For example, the example sentence for 睡眠
「あのボランティア団体は睡眠状態にあり、活動はほぼしていないそうだ。」
That volunteer organization is in a state of dormancy, with very little activity taking place.
dormancy is not a common English word to my knowledge.
Hey I get it, I’m not a native English speaker myself and there’s been a few situations where I didn’t know the English word either, which threw me into the state of actually learning two languages at once 
That said, while I probably haven’t ever actually encountered the word “dormancy” (or at least I don’t remember), “dormant” is pretty common so one could probably guess dormant → dormancy to get a rough idea
I’m native in English and never thought I would encounter that word. There’s a lot of English words I come across on this site that I have never heard before lol.
One of the most valuable lessons I got in one of my translation classes was “just because you don’t know the word doesn’t mean others don’t”. Just because a word is unfamiliar to you does not mean it should be off limits for translation.
Dormancy is plenty understandable and it is, in my opinion, one of the most beautiful things when I get to learn more about my own native language through the lens of the language I am learning.
I never said it shouldn’t be include in translation. I just never heard it, which makes me not know the answer to the example sentence.
As a native speaker, I have learnt so much new English by learning Japanese