I don't think that's true with all change-ups. I'm having success with one of my pitchers throwing a knuckle change just like she does her fastball. Catching for her I see her really selling it as it looks just like her fastball delivery, brush and all.
Agree. There is more than one way to skin a cat. DD's PC just prefers that method and it seems to be working for DD right now but she's admittedly just starting what I hope will be a long pitching odyssey.