What an egregious mislabeling.
Data -> Chats and actual Identity
Metadata -> Who with whom and when from where,...
They construe payment info, PII and similar except chat contents as metadata and say metadata of metadata was that which is normally called metadata. And that it was safe to share despite this obviously being not true.
Everyone remembers https://www.nybooks.com/daily/2014/05/10/we-kill-people-base...
?
How does one understand the authors motivation?