Translation:The breakfast: bread, butter and coffee
That's the point: you are learning French little by little and should not adjust your translations to your usual English, ie with words that you don't know the back translation of.
The more faithful to the original sentence, the better.
For your information: "mon petit déjeuner consiste en:..."
Your point would be well taken if the point of the translation was to make it as conversational as possible. But it isn't. The point is to translate what is there as accurately as possible as long as the sense of it is carried through.
In this case, what may well be a list is provided for you to translate. The apparent list says.....the breakfast: something, something, something. Changing the list to make it more friendly or make if flow better by adding a couple of words is a nice thing to do but is not included the example given to translate. Many English speakers would do exactly that, improve it by adding a couple of words, but would not if they actually didn't want it to be friendly or were supremely indifferent to flow.
Without any context, we don't know whether or not the author wanted it to be abrupt or to put people slightly off or even if he can or can not write natural sounding phrases. All we have are some words to translate. It is not misleading or confusing to translate them as they appear.
It's pretty judgmental as when to apply more natural English and when not to. Sometimes Duo will let you dress it up a bit to make it seem more natural and sometimes they won't. Sometimes they seem to conclude a perfectly literal translation is so awkward that they require a better equivalent in English. Often their choices when to do either don't seem logical. I presume they have more than one person making the choice.
All you can do is curse the green owl and let it go. More often than not staying with a literal translation will keep the heart stealing hibou at bay.