Academics in China - promoted via connections
I am a postdoc in China, and have been here since almost 2 years. I am looking forwards to leaving mainly because I cannot cope with their cultural ways at work, e.g. how the local academia works. The supervisor mentioned in this question does speak the truth about gift authorships in Chinese science, thus firstly let me acknowledge his sincere contribution and advice. As another answer states clearly, ultimately such decision lies in the hands of the true first author and his/her advisor. However there is the conflict of standards over international ethics and clan-specific ethics. Typically what happens is exactly this: a young researcher gets stuck in a moral dilemma with collaborators and is advised to either abide or walk out. The problem is, too often morally questionable standards are not announced before a project starts and abusers rely on the lateness of the dilemma to push for a win-win situation. Adding to the problem, Mainland Chinese people are culturally prone to speak through contextualised subtle insinuations, leaving a lot of margin for belated misunderstanding when dealing with other cultures.
Surely by this point a decision was already taken on this specific conflict, but I will leave here the main advice to others in potentially similar situation. Gift authorship from my experience seems widespread in Chinese academia. Engaging in scientific collaboration with Mainland China academics is therefore prone to lead to conflicts over ICMJE and similar guidelines on authorships and other aspects. This is not to say gift authorship doesn't take place elsewhere as well, however the local approach tends to be more straightforward and intense than elsewhere (i.e. absolute zero intellectual contribution; numerous added names; openly offended if denied). As I believe supporting parasitic academics rapidly leads to bad quality science and somewhat kills the original meaning in the career for most people involved, I refrain from providing gift authorships as best as possible while always reciting the international guidelines. I hereby recommend other serious colleagues to do and preach the same, even if some conflict ensues.
I think that what you have mentioned is relatively common in China. This view is partially based on my experiences and what I have learned from others but also backed up (a little) by some research. Overall research suggests that networks may be more important in China than in the western world. The concept of guanxi is frequently referenced to explain this. Similarly, based on measures of culture, such as those outlined by Hofstede, China and the west are quite different in terms of power distance and individualism. Specifically, Chinese culture has been argued to lead to Chinese people being (relative to Americans) (i) more clearly divided into social hierarchies (e.g., peoples status has a bigger influence in social setting) and (ii) more focused on working toward group success rather than their own individual success.
From your friend's supervisor's perspective, it makes perfect sense to leverage his network through this form of reciprocity. Basically, he does something for these professors, wins their favour and then expects that they will eventually do something for him in return.As they hold more power then him, they may potentially be able to open doors that otherwise would have remained closed (for example through recommendation letters, or personal influences). Indeed, many of these professors may have acquired their position partially due to their own networks, and similar practices in the past.
I think your friend should accept that this is the way that things will work if he continues to work with this group of researchers. If he is too principled and reliant on autonomy to tolerate this then he will need to leave and work with someone else. On the other hand, if he can tolerate this for a while, he may very well end up being the beneficiary of similar behavior in the future.
I think the current answers are not worded strongly enough.
Going along with this is VERY HARMFUL.
Giving a gift in expectation of return makes your friend dependent of these people, whose motivation is already under question.
It is rare to point fingers to unsavory scientific practices in public, but people have eyes and ears. Getting associated with a clique that elevates the connections over honest science will tarnish your friend's reputation.
Going along gives a little bit more power to the group of people who abuse power. Nobody benefits in the long term.