I think that's misworded. The actual quote from Phyllis was " I always carried knitting because my codes were on a piece of silk". There's no need for knittin

I think that's misworded. The actual quote from Phyllis was " I always carried knitting because my codes were on a piece of silk". There's no need for knitting to be involved in the encoding. She had a message (unclear if it was a message she received or her own personal knowledge; likely her own knowledge from observing Nazi/German soldiers), and she had a silk with the code keys, and she had a transmission station.