Yeah...Snapefen use that as an indication of Snape's wonderful teaching skills. Despite the canon statement that Harry felt more relaxed, and Neville looked happier in the Potions practical OWL than ever in Snape's class. When a kid is more relaxed in an exam than in class it's not a good sign. Snapefen don't get this. Harry passed his exam in spite of Snape, not because of him.