I think this is about right, but one sticking point I've found is: what kind of employee is the project manager? Who do you hire, what is the career trajectory? There is a temptation to have them be a manager, because hey, manager is in the name! But having gotten over that, there is a version of the job that is essentially entry level work; what you describe of managing the tickets and all the stuff is just not very high level work relative to what the rest of the team is doing. But then what is the progression? What are they trying to do after they've put in their years wrangling tickets? I think this can actually lead to a lot of unnecessary complexity. If you have a smart and ambitious person doing this job, they're going to naturally look for ways to make it more meaty. But it doesn't really need to be, so you're in a bit of a bind.

I think this is where the impulse to let the managers handle this as a small part of their job comes from. It's already clear who the managers are and what their career progression is, and handling stuff the team needs to unblock, which doesn't fit well into any particular box is already part of their job.