It’s a great demonstration how unrealistic it is to use it.
If it is this complicated for a demo project for the purposes of the book, in my opinion, it shows it’s completely inadequate for handling anything remotely real.
Project ongoing for five years, 10 devs on the team, each year two resigns and two joins, some good, some mediocre, can you imagine them mess this will be? And that’s not even a large project, it’s just an average but real project size.
KISS / YAGNI goes a long way.
I also think it's bad to create this many diagrams at this level of detail, or try to keep the model updated, in an active software project. I think it's important to be selective—sometimes that even means choosing not to choose.