This text is from a transcript of a talk by David Gooding, entitled ‘Unity, Origin and Victory’ (1987).
Yes, exactly right. If you are reading an Authorised Version, that was the device that the translators used when they put in words that weren't in any Greek manuscripts whatsoever. They just put them in to help out the sense. The translator is adding a word to try and bring out what he thinks the sense is. But the fact they put it in italics means that they didn't find it in any Greek manuscript whatsoever: they are adding it as translators to help out the sense.