Spaced repetition and flashcards are two very different things. It is very unfortunate that people are constantly confusing them. Spaced repetition is an idea that you recall/revise in intervals. Flashcards are a method to learn/revise by flashing card on you which is not exactly the most effective learning for me.

Mentioned Duolingo has spaced repetition. It is not a flashcards app.

For me as an adult who did learned stuff, both the supposed frictions and necessary components of learning as described in the article does not ring true. It is not really consistent with how I perceived anki/duolingo nor how I understand the reasons for "create own cards" advice. It is not even consistent with where my learning successes and failures came from.

Maybe I am simply not the target of this startup then. But also, I do not think I am the only snowflake adult for whom these points did not ring true.