Those are different time periods and different purposes. The Deuteronomy 13 is ongoing, 1 John 4 the final test . Just like the Deuteronomy 4 used to protect the integrity of a single word seeing change the meaning of a single word changes the authorship.
While the Revelation 22 the warning as the last commandment of God it is in respect to the whole or the perfect .(Do not add or subtract) Nothing missing. ...
None of which answers my earlier question to you...
Where is this following, your earlier post, written in Scripture?
Its how we try the spirits to see if they are of God not seen or men seen . If any man say I have seen the Lord, heard audible voice, or had a dream as a personal experience we are to believe not.He warned us before hand.
Further, neither the passage in Deuteronomy nor the passage in 1 John has anything to do with "protecting the integrity of a single word"; that idea comes in the last chapter of Revelation, and likely refers only to the book of Revelation.