I don't think they have to explain their decisions to anyone - they're free to cover whatever drugs they want on whatever tier they want - if you don't like it get insurance from someone else - impossible if it's via your employer. Anyway, reason to put GV on a cheaper tier than V is obvious, they pay less to cover the scrip - they don't care if the patient will pay more out of pocket if they can't use the coupon anymore.
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