“This telegram must be closely paraphrased before being communicated to anyone”

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 by the use of synonyms and synonymous expressions. In this process, deletion rather than expansion of the wording of the message is preferable, because if an ordinary message is paraphrased simply by expanding it along its original lines, an expert can easily reduce the paraphrased message to its lowest terms, and the resultant wording will be practically the original message. It is very important to eliminate repeated words or proper names, if at all possible, by the use of carefully selected pronouns; by the use of the words "former," "latter," "first-mentioned," "second-mentioned"; or by other means. After carefully paraphrasing, the message can be sent in the other key or code. (b) Never send the literal plain text or a paraphrased version of the plain text of a message which has been or will be transmitted in cryptographed form except as specifically provided in appropriate regulations (emphasis mine) In fact the allies would have have known intimately about how this was possible, because this is one of the ways they ended up decrypting the stronger German Enigma cipher. Captured machines using simpler ciphers were used to break those simpler ciphers. The fact that the Germans were encrypting the exact same messages in both ciphers meant the allies could know (for those messages) what both the unencrypted and encrypted messages were, which allowed them to decrypt the stronger cyphers as well, or quickly figure out what today's code was.