It's not at all extraordinary to assert that another has errantly characterized the nature of one's own and own organization's activities. Nobody I know of cares to be misrepresented, most especially in public situations that matter, in any way, shape, form or measure. Maybe folks you know don't much care about such things. I and my cohort do.
Perhaps you've seen the phrase I use on DP to indicate that someone's mischaracterized me and/or my remarks? "You just keep thinking that..." That's what I say when the circumstance(s) merit not my going into more detail. Carr's remark is only slightly more illuminating than the one I use...No surprise that, for his situation doesn't allow him the glibness of the phrase I use on DP.
Though I identified one of the Buzzfeed passages that I think may be what the SC had in mind, it could well be that it's not those passages at all and that it's, for instance, Buzzfeed's claim that its characterization of the nature of evidence Mueller has as having come from Mueller's office when the fact is that it didn't. As I said, Carr's statement was "beautifully" ambiguous.
ETA:
What my earlier post assumes is that something leaked out of the Russia investigation and Mueller thus had to respond to it because, unlike everything else we've heard about the SC's work -- all of which came from witnesses, their attorneys, and Mueller's court documents -- this is alleged to have come from his office/the DoJ.
It is ENTIRELY extraordinary for the Special Counsel's office to do so.
To think that they would do something they almost never do just to nip at the fringes of a news story that's basically correct strains credulity, to say the least.