In math, there are many "proofs" that 1 = 2. Going through them and picking them apart is a useful exercise, and can expose misunderstandings and mistakes that are important to be aware of. But at the end of the day, nobody really seriously considers that 1 actually equals 2, it's too at odds with everything else we know.

This article is saying that it's possible the FT piece found a valid nitpick, but that the conclusion they're fighting against (rising wealth inequality) is backed up far too strongly by other independent sources for a nitpick to damage it at all.