I am not a teacher.
That is a very interesting analysis leading to a surprising conclusion.
I had to think about this a bit because you seemed to be right but at the same time it's not possible for the second person plural to only include the first person.
What I think the "may not include" part actually means is, "include specific people (not just anyone)".
In other words it doesn't include the first person and may include everyone else or just some others. Or am I completely missing the point?
Student or Learner