I don't buy it...damaging the bore that is.
But it would be possible (and easy) to damage the crown with a rod or attachment.
That said I have not used a "rod" in over 20 years...Back about 1986 or 87 I bought one if these... MidwayUSA - Otis Deluxe Rifle and Pistol Cleaning System
I still have every piece...my wife bought me a new one for Christmas, but its still in the box...I'll leave it there until the old one breaks, which I don't see happening for a long while yet.
20 years of clean, undamaged barrels for $20...what more can I say.