In my experience due dates mean absolutely nothing.
I also had Grant Review Ready PM03. As far as I know, PM03 is more senior than PM01, so your application may collect dust longer, until it gets to one of them for the review.
For me filing mandamus helped IRCC to find motivation to get a PM03 to review it within a couple months, no idea what would have happened if I just waited.
The assignment section may mean that either it is not assigned, or that the employee who redacted the notes randomly decided that you don't need this information.
I had an agent assigned since February with a due date in April, but there was zero movement on my application until I filed mandamus in June.
So, maybe not having anything in the assignment section means that assignment is not done yet, however, having something in it doesn't mean that the application will be processed any time soon.
I only reached that stage after 19 month of processing though, so I think you timeline is not so bad yet.
I don't think I've ever been assigned to RC-8090 after the test, so no idea about that one.