One other (totally unrelated) thing I noticed after doing my first lessons:
I set the Locked Item Position to “Last” (in the settings) and now I get this:
The thin black border should also move to the front, I guess? Because those are the items that will get completed first.
EDIT: After I did the next round of reviews, I noticed that the ordering of the kanji “in progress” is also a bit confusing to me. When the Locked Item Position is set to “First”, the order of the kanji is increasing, i.e. first the locked ones, then the Apprentice I ones, then Apprentice II and so on. So when I set the Locked Item Position to “First” I expected the kanji order to be reversed, i.e. show the locked ones last, then the Apprentice I ones before them, and the Apprentice II ones before those and so on. But in fact the order of kanji remains increasing, just the locked ones get moved around. (This way, even moving the black border to the front does not make much sense because it does not indicate those kanji that will be the foundation for leveling up anyways.)
To fix these issues, it would make more sense to me to display the kanji in descending order and to move the black border to the front. (A more radical option might be to remove the confusing “Locked Item Position” setting altogether… 
)