I already gave you the true answer, it was just massively oversimplified. Let me expand, to save you the trouble of searching the internet: the priorities of Chinese planners and engineers doing things like subways focus on technical aspects (structural, dodging other in-place infrastructure like pipelines, the functional stuff that has to be stuffed in, etc.). The attitude is that the facility is what it is, and the users need to adapt to whatever the facility ends up. This also holds true for most public buildings, although the element of "edifice complex" additionally comes into play there.

Hong Kong, Tokyo, and most Western countries take the opposite approach. They first look at user needs and take into account natural movement patterns of humans, then design the facility infrastructure around that. Of course there are some compromises you have to make with technical requirements, but you end up with a far more passenger-oriented system. Sheer volumes of people is actually pretty irrelevant as an excuse or rationalization of a less-than-optimum system. I don't let my fellow professionals off the hook that easily.

A lot of this has to do with how Chinese professionals have been trained for decades--mathematical/technical only and little or nothing on the humanistic side of physical facility and infrastructure planning. Also a governmental/organizational cultural bias that truly does not think passenger/user hardship and inconvenience is any problem.