Are one time pads still secure when using randomly generated words as the pad? I was researching the US military's DIANA one-time-pad system and came across the following quote purportedly from a former US Special Forces soldier: 


  Special Forces were one of (if not the only) units in Vietnam to
  utilize Morse code on a regular basis. We used a method of encryption
  called the Diana Cryptosystem.
  
  The basis of these one-time pads, is that there were only two matching
  pads in existence, and they would only be used one time. They were
  booklets that contained randomly generated groups of 5-letter words,
  30 words to a page. The person sending a message would first write the
  letters to the message, over these random groups of words. Included in
  the front of each one-time pad was a one-page encryption table. If I
  wanted to send the letter P, and the letter under the P was an A, then
  I would send a K. The person listening on the frequency at the other
  end, would have the other matching pad. They would write the letter
  they received (a K) over the letter in their one-time pad (an A), and
  decipher it based on the table, yielding the original letter P.


(source: https://dodona.ugent.be/en/exercises/2088793301/)

Wouldn't the use of random words as reported by the soldier rather than groups of random letters diminish the security of the system, as the letters in 5 letter English words are not randomly positioned? 

I am aware that "secure" in this context--messages between Special Forces camps during wartime--may just mean keeping messages secure long enough that they are no longer useful even if broken.
Do those look like English words to you?

WHTVI AUCFU RETFK OMSAL
MYMNE ZIEGP UKVTF WZHOK


(Quoted from the page.)

When they say ‘5-letter words’, they don't mean words chosen from an English dictionary.  They mean that they rolled a d26 five times independently and strung the resulting letters together, with spaces between every five letters and line breaks between every four ‘words’ for legibility.  This method is just as secure as using a d2 (i.e., flipping a coin) to choose the bits of a binary one-time pad; it just uses a different alphabet.