Could students do the proposed assessment(s) well but not really have mastered or understood the content in question?
Could students do poorly on the specific assessment(s) but really have mastery of the content in question?

Could students do all the designer-proposed activities in Stage 3 but not really be ready to explain/ justify/ infer meaning or transfer their learning as demanded by assessments in Stage 2?

Could students do all the proposed activities in Stage 3 but still be ready to handle tasks in Stage 2 that require higher-order inference and other kinds of meaning-making?