I think she's full of hooey. It's the needle that moves from side to side & that has no effect on the walking foot UNLESS the opening is not wide enough to accommodate this movement. I have had a Bernina 820, several Singers & I now have a Husqvarna Viking Designer EPIC & I have done this with all of the walking feet & have never had an issue with any of them. I also know someone who thinks she knows everything also & trust me, they don't. No one knows everything but it's very seldom that anyone challenges them so they continue with their behaviour.