What kind of footing is your horse living and working on?
There are varying thoughts about scooping.
Some say if you’re regularly working and living on softer sandier footing that’s “squishy”, then scooping can allow some of that footing to “squish” out the sides of the foot and not pack so much up into the foot. I don’t know how much of that I believe.
Some say that “scoops” are a natural byproduct of following the contour of the sole, which I have seen in some horses that don’t have as much of a ledge of sole around the quarters, as they do around the toe.
I have personally done small scoops for reasons Hightale said - help relieve some flaring that has developed. Most of the time the flaring is trim-caused - underrun heels, overgrown bars. But I have 1 horse who is permanently lame in his LF, and it affects how his RF and RH are bearing weight, and the RH especially now tends to develop weird flares due to how he positions, weights, and unweights that, so if I see some flaring develop, or chipping, I’ll scoop that quarter for a few trims.
Scoops to the point they are forcing heels, and just the toe, to bear weight, is too much. They’re scooped too far back. It doesn’t take much to create a scoop to affect whatever you’re trying to affect.
But also, scoops don’t leave heels too long. Heels are too long, or they aren’t. But if this farrier is scooping to help with flaring caused by HIM leaving heels too long, and/or bars overgrown, that’s a farrier issue, and not likely something you can get him to correct, because he either doesn’t see it/know how to do it properly, or he doesn’t care
But, the first step would be to say to him - hey Farrier, I’ve noticed that my horse’s heels are really starting to chip around the 2 week mark these days, what do you think could be causing that?
And then see what he says.