I think the term "dummy silicon" is fair because those wafers don't have any transistors or wires on them but OTOH they also cost almost nothing so it's not as wasteful as it might sound.
Yes, they are bonded (glued-on) chunks of silicon with no logic. That is the definition of Dummy Silicon. The person who wrote the report is a professional chip analyst who does die deconstruction.
I think the term "dummy silicon" is fair because those wafers don't have any transistors or wires on them but OTOH they also cost almost nothing so it's not as wasteful as it might sound.