Most of the difficult enemies of the game do not count towards god kills when they are killed. These include monsters like Kage Kami, Stone Guardians, and more.
Solution: Filter all enemies to see the ones which have difficulty comparable to Godlands monsters and other monsters such as Lizard God and make them count towards god kills. Also, most mobs with base HP above 1000 should probably count towards god kills. Ent Gods and Ghost Gods have 1000 HP and simple behaviours. Lizard God has even less.