Anytime a writer tackles the live of someone who lived more than 400 years ago a certain amount of supposition is necessary. The amount of supposition increases exponentially the farther into the past and the less prominent the person. Julia Fox's biography of Jane Boleyn (Anne Boleyn's "infamous" sister-in-law) is a prime example.
Where some writers would either boldly present supposition as the most likely thing that happened so let's just go with it, shall we? or skip the supposition altogether sticking to the dry facts, Fox feels compelled to let the reader know she's taking an educated guess. The words "possibly", "perhaps", and "maybe" thus get quite the workout, as do the phrases "may have" and "might have" and "we can't know for certain."
We can't indeed, dear Julia, but that hasn't stopped thousands of historians from guessing so buck up and be a little bolder, ok?