With hostilesIgnoreHostileIdentityPlayer set to true and tested on Fabric 1.18.1. (mod .jar file is identity-1.16.0-1.18.1)

When an entity-based ability damages or kills a hostile mob or two, only the mobs hit will be aggro'd.
This can result in easy cheese kills in an enemy-crowded environment as long as normal player attacks are not used.
(Creeper's Explosion, Blaze's Fireball, etc.)