Why does vocab track how many are unlocked instead of how many are passed

If you want to track your vocabulary progress, then consider using the WaniKani Dashboard Level Progress Detail 1.0+ script. This script adds a vocabulary progress bar near the existing radical/kanji progress bars on the dashboard.

I also don’t like moving to the next level without completing the current level’s vocabulary. Therefore, I use a lesson reorder script (like Reorder Omega or Wanikani Lesson Filter) to keep my kanji and vocabulary lessons approximately balanced percentagewise.

This “Amount of old lessons when starting new level?” thread and my post in the thread provide more detail. The thread/post explains some options for how to slow down a level up AND/OR keep the kanji/vocabulary balanced.