Does 'This explains the presence in Guangzhou of the Huaisheng Mosque, reputed to be China's oldest, and traditionally dated a.d. 627.' provide a contradiction to the established premise 'The Huaisheng Mosque is China's youngest mosque.'
This explains the presence in Guangzhou of the Huaisheng Mosque, reputed to be China's oldest, and traditionally dated a.d. 627.###The Huaisheng Mosque is China's youngest mosque.