Your surprise at the comments about "sanding the damaged part away" show your lack of understanding of composite repair techniques.
Gosh, that's told me.
And to think that I turned down the chance to buy shares in that sandpaper manufacturer.
But I suspect that whatever repair technique and materials are being used, cutting out the damaged structure doesn't just involve a bloke with a Black & Decker and a few sheets of abrasive, wouldn't you say ?