I’d say that the usefulness of the mini stories largely depends on the language. I wouldn’t doubt that whoever created the original ones put some thought into them. But to me it always appeared as if they then just get translated into the other languages, with only minor modifications made. This isn’t a big deal if the language translated to is similar to the original language, which I suppose is English. But if the differences get bigger, all thoughts that might have originally put into it don’t play out anymore.
The first language I have used LingQ for was Spanish. The mini stories were okay for that language. The difficulty was gradually increasing and the idea of telling the same story from different perspectives was useful, too, as Spanish features verb conjugation. It is also useful to have Q&A if the word order in statements and questions differ, which is the case in my mothertongue German, too, for example. German, Spanish, Russian etc. are all european languages, though, and as such feature a lot of similarities.
The second language I have started learning and am still learning is Korean. Korean doesn’t feature verb conjugation in the sense that you have to modify the verb depending on the person who is performing the action (1., 2., 3. person singular/plural) and the amount of tenses is relatively low. But the verbs get modified based on the status of the person who is performing the action described by the verb as well as the status of the person you are talking to and the situation you are in. Some verbs get replaced with others if the person performing the action has a high status. In addition, auxiliary verbs are commonly used. On the other hand, if there are no differences in status, it doesn’t play a big role from which perspective a story is told. So the repetition in the mini stories isn’t helpful. In addition, there is no difference in word order between statements and questions. So the Q&A part isn’t that helpful, either.
Another aspect that doesn’t even exist in German, English and Spanish (and probably many other european languages) are bound nouns. These are nouns that cannot be used on their own but have to be precisized using participal forms (think of subclauses used like adjectives). The latter are especially important as Korean doesn’t feature relative clauses. However, while bound nouns can be found excessively in all kind of literature, their are quiet underrepresented in the mini stories. There are also many grammar points that describe similar relationships between clauses, but differ in nuances. As those nuancial differentiation isn’t made in the european languages I know and probably many others, they aren’t represented in the mini stories.
In summary this causes many important aspects of the language not beeing touched at all, although fundamental, while redundancies occour beyond usefulness due to the translation. In addition, the difficulty of the stories isn’t neccessarely in the order the stories are presented.
So, I am not saying that the mini stories are complete nonsense and can’t be of use, but they become gradually less useful the more the language you wanna learn differs from English. It is a general issue I think LingQ has, that it is highly English-centered, causing a lot of unpleasencies for those of use who try to learn a language that hasn’t got that much in common with English.
So if the mini stories are mandatory for adding new languages, it would be good if the same thought that have had been put in the original ones would also be put in the new ones, to ensure that the aspects of the language that are essential are really featured.