And if you paid Biz class points and obtained a reward in Coach operated by a *A, you cannot even standby on Biz class. You can only standby on AC metal.

It is a matter of priority. I think AC has set the priority right. As I always maintain, if I owned a business, I would treat my long-term repeat customers better than an occasional customer who buys an expensive item. So Es and SEs should get priority over AP reward users.