Right; that’s the expected and correct behavior - that project setting is only for the default type, as it says, it’s not for a default task template.
You can vote here for having a default task template in a project (oh wait - you already did vote there!)
I agree 100% with you here; I find that part of the task template/custom task type dialog confusing and not-well-designed. It’s a brand new feature, so hopefully they’ll clean that part up.