Hi Tad,
I've not yet had the opportunity to read Quinn's book (though I have flipped through it). Until I do, I cannot say for sure if the material Quinn wrote came directly from Williams' memoirs. Williams gave interviews over the years so it is impossible to say for sure at the moment.
Mrs. R. Norris Williams II is still living. She and I did an interview last year for Sports Illustrated Video. I had been writing to her for years but only when I met her did she tell me that her husband never liked to discuss the Titanic. He only wrote his memoirs out of his love and respect for history. He was quite a scholar. Mrs. Williams told me that "Dick loved history but not his own." He was a very private man, and did not like to take part in the publicity later built up over his Titanic experience as well as his successful tennis career.
I will read Quinn's book and let you know what his source was.
Best regards,
Mike Findlay