Obviously he/she's wrong. It's not entirely surprising for some Chinese properties to be quite uninformed, especially the properties which were previously independent hotels that had just joined in the Accor brand by management contracts.

I would write back and insist on the Platinum benefits in a firm and polite tone, failing which ask for the hotel manager's email to escalate the issue. The ones that understand are those that receive loads of platinums day in day out, like Sofitel Hyland Shanghai. The only other positive experience was Sofitel Sunrich Guangzhou, just because there were a lot of French managers seconded there and they were keeping the local staff on their toes.