@EricPreneta Got a response:

“What you’re seeing can happen depending on the study plan type you generated. Different study plans include different subsets of lessons based on your pace and prep timeline, so some of the earlier Grammar lessons from the full lesson library may be skipped in more streamlined plans.

If your schedule allows for it, you’re welcome to switch to a different study plan type (such as Balanced or Comprehensive), which includes additional lessons from the lesson library. You can make that change anytime in your Study Plan settings.

You’re also welcome to complete additional lessons directly from the Lesson Library if you have time and there are topics you’d like to review more thoroughly.”

The lesson starts with "last piece of jargon" from grammar but this is the first Grammar section following the arguments section. Am I missing something?