We don't know the story behind it. For all we know, maybe the Valkyrie owner used to have a Harley, his wife got some horrible cancer and he had to sell everything he could to pay the bills.. then his brother-in-law has pity on him and gives him his old Valk so he could have something to ride. Missing his old HOG so much, he puts Harley (tm) logos on it so he can remember the good old days..
Pretty far fetched, but who knows.
BTW I've seen people putting Harley logos on things that weren't even motorcycles.. like car and truck windows ! the nerve !