Hi!
I believe there was no such claim, if anything, it was pointed out that setting up the stats engine didn't give access to information that was not accessible before by the Checkusers (even if logged), and that most fears of data being handled by the wrong hands are mitigated by the facts that the data was handled by a CheckUser (and thus a) a person already with access to said data and b) a person identified to the WMF and trusted by the community*).
checkusers don't have readership data.
Domas