Why does Leslie Cheung's Putonghua sound like a mainlander speaking Putonghua, even though he can't be recognized as a Hong Kong native?

Because when he was filming Farewell My Concubine, he went to Beijing three months in advance to learn authentic Beijing dialect and practice Beijing opera. His diligent attitude made Zhang Manling, a Peking Opera teacher at that time, highly praise him. Besides, he is a person with super language ability, so he speaks very standard Mandarin. You can go to Baidu. Zhang Manling, a famous Peking Opera actor, recalled "My Forgotten Friendship with Leslie Cheung", which was introduced in detail.