The Testimonium is quite obviously altered, at the least. It’s a shame that some unscrupulous people went and did that, because it casts doubt on whatever might have been mentioned about Christ in the text before the alterations.
Some "Christians" did the same type of thing in those days to the Septuagint, copying back into it the words reinterpreted by Paul and other New Testament writers of the Greek, such that some dim-witted translator/exegetes of today make claim that Jesus and other Christ-followers used the LXX and not the Hebrew texts as their Scriptures, using these insertions a "proof" that LXX was a better and approved version used by the Hellenized Jewish hoi polloi of that day.
This, of course, is a great flaw of the Greek Orthodoxen relying on the Septuagint as a reliable version of the Old Testament (which the English Authorized Version translation does not).