Throat erosion occurs during the entire life of the barrel not just the first few 100 rounds. Thats why they make throat and muzzle wear erosion gauges.
Read the link below.
https://www.luckygunner.com/labs/bra...el-cased-ammo/
Bottom line, heat causes throat and bore erosion and the peak flame temperature of the powder as chamber pressure increases is what causes the wear.
Example a .222 at 46,000 cup or 50,000 psi max pressure will have less throat erosion than a .223 at 50,000 cup or 55,000 psi.