Regarding broach-rifled barrels. . . . .
The ones made at the USA government's Springfield Armory for M1 and M14 rifles as well as the pre-'64 Winchester 30 caliber match barrels, when their teeth were worn down enough to have groove diameters under .3000" shot great from the first round. And the dozens used in 7.62 NATO Garands I've seen and had all had a lot of copper wash after 3000 to 4000 rounds of barrel life even when the copper all got periodically removed with non-embedding abrasives and non-corrosive chemicals. So, I don't think shaving, scraping or plowing off jacket material hurts accuracy as long as it's uniform around the bullets.
Regarding burnishing of premium barrels. . . . .
I've never had a premium barrel that needed any burnishing. They all shot great from the first shot down range. A good shot can sight in a premium rifle using premium ammo with one round anyway; maybe two if he's having a bad day. Even if the sight ain't aligned dead center on the target when it fires.