Most probably, Gao Feng had already known that Yun Xiangxiang came from the mainland and so he spoke to her in Mandarin. Although it wasn't perfect and heavily laced with a Hong Kong accent, the gesture moved Yun Xiangxiang.
Yun Xiangxiang also replied with her half-baked Cantonese, "Yun Xiangxiang, please guide me senior."
No one thought that Yun Xiangxiang could speak Cantonese. It was definitely a little lacking compared to the native Hong Kong or Guangdong Province people, but it was enough for them to understand clearly. This made Gao Feng and Lin Jialiang feel that the little girl was quite interesting.
Since Yun Xiangxiang showed that she had no problem using Cantonese for communications, Gao Feng did not trouble himself. When they filmed, they must be conversing in Cantonese lines, "Why don't you pick a part for us to practice, we'll familiar ourselves with each other first?"