Wie schon gesagt bzw geschrieben ist mir kein Explorer bekannt der sowas kann oder macht.
I don't remember it completely but I believe I read about the connection on their own website! In other words this has never been something they hid!!! So why is it being treated as a new thing and "leaked documents"?
Here is another post from someone else in 2017 (quoting the footer of the website):
https://bitcointalksearch.org/topic/m.21163750
Here is another quote from 2016
P.S. Any centralized service including blockexplorers, exchanges, etc. are honeypots whether they are owned by a blockchain analysis firm or not.
Zudem benutze ich diesen nur für nachforschungen bei hacks oder anderen Sachen.