there is a difference between high school STEM and elementary, for example, and those appear to have a natural break point. i don't know why my wife, who has a preK-3 "certification" isn't "certified" to teach 4th grade. Or if she's taught special ed for 10 years she's not "certified" under state law to work in special ed in a different capacity.
Do you think police should have different certifications to work with white people, black people, poor people, rich people, immigrants, etc? No. But the claim that since kids develop differently you need to protect everyone with dozens of "certifications" is really no different that any other profession working with diverse people.