Guo Tiancheng's words amounted to an invitation. Although the invitation from Guo Tiancheng seemed casual, Nie Zhenbang was very clear that this was also a probe by Guo Tiancheng. Only by broaching the subject in such a way could there be room to backpedal.
At this level, one's image and other various aspects required careful consideration and deliberate thought. This was not a level at which one could act impulsively. Many situations demanded caution. For instance, right now. If it were a formal invitation and Nie Zhenbang failed to show face, Guo Tiancheng would naturally lose face as well. By phrasing it this way, such an outcome could be avoided.