Not an expert but my reading of the article is that the Book of Hours/Hardouyn Hours was a Catholic prayer book in Latin and Thomas Cromwell was a secret sortof proto-Protestant who had illegal copies of the english translated Tyndale Bible hidden at his home. So the jewel encrusted latin prayer book might have been a cover story of a sort. As in, I don't think the prayer book in the famous painting reflected his actual (hidden, illegal) religous beliefs.