I think it's a case of deleting all pm's by this "person" not just in the boxes of those who reported that particular person. I too received the same pm, but didn't report it before Justin had deleted it from my personal inbox.
It's not a point of Justin reading the pms, it's the fact that he's had enough complaints about this particular "member" and has deleted all the pms from that particular person, I would think.
But I would also add that, as an administrator, I would think the EOS team could read any PM if they wanted to, so long as they had the right access. That's a privilege/right that comes with being the website owner/administrator. As to whether they would or not, that's a different matter!! EOS also has a responsibility to their members and others, so (again, I would think!!) obviously has access to what is stored on their server. Any company has access to what is stored on their server, in their employee's email accounts, etc!!
Again, just my opinion, but seems logical!