i usually see this as "<journalist> confirmed the source's authenticity", or some variation. the difference between that familiar phrasing and the one here was enough to grab my attention. that the journalist knows (currently) the source's "identity" is not the part a reader cares about: that the journalist confirmed (past tense) the "authenticity" of the information they're reporting is. most probably i read too much into the variation of phrasing here: editor's acting under time pressures, and all that.