为何大学需要update我陆本的medium? 如何证实?

今天committee发来一个email,
we would like to follow up with you regarding your current employment status/internship plan and official documents which certify the medium of instruction during your study at (陆本),

我不太确定我当时有没填写我的陆本是一半中文一半英文授课了. 但大家有遇到过这个问题吗? 该如何证明the medium of instruction?

而且, 我已经有美本几年了, 按理说陆本无论有没英文授课也不影响啊. 难道是因为我要求toefl waiver?
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