edit: The recent adobe email list comes to mind.
What you describe is exactly the exploit that was disclosed and exactly what the person exploiting it seems to have done based on the content of the list. Of course, Coinbase argues that this is a feature and not a bug.
That doesn't really mean anything, since it clearly says at the top:
"Here is a partial list of Coinbase user emails and their full names. Full list much bigger."
Which could be bullshit and scaremongering. But it certainly could be true that they have a large number of Coinbase user's emails.
It could also be that you are reading too much into it.
>"Here is a partial list of Coinbase user emails and their full names. Full list much bigger."
Where does it say in that sentence that he the OP has access to the "full list"? It doesn't say that. It implies it, which you picked right up on. But he doesn't explicitly say, "Here is a partial list of the full list in my possession".