"This telegram must be closely paraphrased before being communicated" Why?

Summary

It appears that it was US military communications doctrine to not send the exact same message twice using different encryption ("none" counting as one type of encryption), and the term of art for changing a message to avoid that was indeed "paraphrase". I managed to dig up a US Army document on Cryptology from roughly that era that appears to discuss paraphrasing. The document in question is Department of the Army Technical Manual TM 32-220(pdf), dated 1950, titled "BASIC CRYPTOGRAPHY". It apparently supersedes previous documents TM-484 from March 1945 and TM 11-485 from June 1944. It would probably be more ideal to look at them, since they are closer to the time you are interested in, but I was not able to find them online. Here's what this declassified manual had to say about "paraphrasing", from Chapter 7, in the section Fundamental Rules of Cryptographic Security, section 84, subsection b, rule 3 (titled "Text of messages") (a) Never repeat in the clear the identical text of a message once sent in cryptographic form, or repeat in cryptographic form the text of a message once sent in the clear. Anything which will enable an alert enemy to compare a given piece of plain text with a cryptogram that supposedly contains this plain text is highly dangerous to the safety of the cryptographic system. Where information must be given out for publicity, or where information is handled by many persons, the plain text version should be very carefully paraphrased before distribution, to minimize the data an enemy might obtain from an accurate comparison of the cryptographic text with the equivalent, original plain text. To paraphrase a message means to rewrite it so as to change its original wording as much as possible without changing the meaning of the message. This is done by altering the positions of sentences in the message, by altering the positions of subject, predicate, and modifying phrases or clauses in the sentence, and by altering as much as possible the diction b...