But conversely, if I alt-tabbed to chat with a friend, or paused studying because the person sitting next to me asked a question, or I took a sip from my coffee mug, that doesn't mean it's hard necessarily. Even though all of those take at least as much time as answering a hard card un-interrupted would.
The AI cannot read my mind, there is no approximation that will work reasonably accurately here for "how confident was I in my answer", unless I input that myself.
I would argue that it's harder for me to decide how easily I recalled a word and decide between a few loosely defined levels as to which one I should choose than to apply a simple algorithm.
If the window loses focus it would be able to pause automatically. If you are distracted another way, no big deal you will see that word again soon and unlikely to keep getting distracted on the same word. The benefits would outweigh the odd misfire.
For me to put a foundation for French down it was: Assimil for about 6 months (30 min/day), 30 minutes of daily comprehensible input, and Anki & Clozemaster for vocabulary (~15-20 min/day). Mixed in there was a couple months on Yabla doing listening comprehension, some grammar study from Bescherelle books, and some tutoring on iTalki. After about maybe 9-12 months I could listen to RFI's broadcast targeted to learners [2], but even then I still needed to go to the transcription a lot at the beginning.
To mislead people into thinking that doing some vocab study for 30 min a day in Duolingo is going to get them anything beyond the most basic grasp of a language is kinda not cool.
[1] https://www.state.gov/foreign-service-institute/foreign-lang...
[2] https://francaisfacile.rfi.fr/fr/