This seems to be somewhat of a regional thing. I rode in SoCal (predominately Hondas) for over thirty years, and your description is accurate for that area. Then I moved to Colorado (four corners area), and the Harley riders here wave just as often as the GoldWingers. There are also MORE Harleys than any other machine here.
They don't mistake me for one of their own, either -- I'm on a silver Honda ST1100 wearing a white helment and an Aerostich suit. :)