only cancel natural entity spawns

I made a sort of infected version of a cow and I want it to spawn instead of cows naturally.

I have sort of pulled it off with a procedure that's called on the "Entity Spawns" global trigger, and it checks if the entity is a cow and if it is it spawns the infected cow and cancels the event so the normal cow doesint spawn. But it does this when a cow spawns in ANY way but I want you to be able to spawn normal cows from eggs and mob spawners.

I only want to replace the cow when it is spawned naturally by the world.