There's incertitude for you. My surmise is that Novick is trying to support his hypothesis of James' initial sexual experience, and that he picks the name handiest to him. Novick seems to want to link his two subjects. It is clear the homosexuality doesn't bother him. He simply wants us to know that James was a sexual man and a loving person.
Biographers often develop strange attachments to their subjects.
It is based on James' letters from Paris between 1875 and 1876. He has met Ivan Turgenev, the Russian master, and finds himself moving among assorted Russians. One of them is Paul Zhukovski, son of a Russian poet who tutored Alexander II when he was a prince. Reared in the royal court, Zhukovski is soft, dependent, spoiled, and weak-willed, but graceful and entertaining. They dine with Turgenev, and with countesses, a duke, princesses.