This could also just be a simplification for the purposes of this announcement.
They mention this being mostly about security and preventing the use of hacked accounts, and they mention these dormant accounts that were only created and then went immediately dormant. It makes sense to me that they are in fact talking about this issue, just not explaining all the detail.
Especially given you're talking of "thousands" of accounts, I suspect whatever problems mattered to you the most were not the same as those of Google's account system.