Not so sure I believe this, because even the Bible colleges I've attended have taught differently, as have most of the pastors I've had when they're describing these texts.
The Sinaiticus is a fraud, it was written between 1839-1844 to get a printing press from Russia. In order to give it credulity by the guy that stole it, a letter was made up referring to the Septuagint which also didn't exist. The ink this was letter was written with didn't exist until the 1800s. There is no chain of custody before the 1840s. Have a look at it on their website and you will laugh at how amateurish it is.
https://codexsinaiticus.org/en/manuscript.aspx
Are you positive the underlying manuscripts of the critical texts are the same as the RT on this, or is there an intentional misrepresentation by most KJVO's? Asking in all sincerity. I've looked it up before, but that was many years ago....still, I would go by the totality of the text instead of just one part of the passage.