Just quote what I was told by CX customer care:
Please be advised that passengers originating their journey from Hong Kong or the Chinese Mainland, departing from Orange zone (all destinations except Chinese Mainland), are invited to visit The Pier, Business (as per their Oneworld eligibility).
Passengers shall be invited to The Wing, First if they are travelling to destination - Chinese Mainland, as The Wing, First is the only lounge located at the Green Zone. As your journey originated from Hong Kong to travel to Kuala Lumpur, you would have been able to access The Pier, Business lounge.