Thats pathetic..i have door sills on mine, but its not something i would think of telling them about. Its just like..would you tell them about having a sticker on your rear windscreen? Because that effectively does more harm than door sills. Insurance companies are a bit of a pain tbh because you never know what they actually class as a modification...
As i previously mentioned, stickers could technically be a modification, but you would never think twice about phoning someone up saying "hi, i've got a small sticker at the bottom of my window, will you insure me with it on"