I think it doesn't since mobs that are summoned by an amount of only 1 don't get affected by this conf value:
if (mobspawn.num > 1 && battle_config.mob_count_rate != 100) { if ((mobspawn.num = mobspawn.num * battle_config.mob_count_rate / 100) < 1) mobspawn.num = 1; }
Thanks for finding the source. I tried and it really doesnt count the MVP. This trick is neat when want to change MOB RATE. Thanks!