I think that is Amberley's influence regards the title as their Tudor biographies tend to have subtitles. I haven't read the book as yet but I believe Loades looks at the wider picture of Tudor politics with regard to Henry's match with Catherine Howard so to subtitle it as such is a shame and may mislead. The subtitle will help it sell which, in my opinion, is Amberley's primary objective.
I too am a Loades fan as you will see from some of my reviews of his books. I think you'll also enjoy Richard Rex even more. His books on Elizabeth and The Tudors are superb!