The OP referenced Kennedy, who sells DSG Girdles. DSG's website states "The kit contains a CNC-machined, powder coated set of girdles to tie the three middle caps together."
So I would say the manufacturer says they are. If you look at the picture, it looks like the entire girdle is black.
I looked at the DSG picture I would guess its not powder coated,and it says nowhere that it is. I'm afraid somebody misled you. I would think anybody that designs a girdle would be smart enough not to powder coat or paint it ,especialy on the mounting surfaces.