The context here is growth and I doubt China's GDPPPP/person has grown anywhere near as much as its GDP/person because the median Chinese household of 40 years ago could still afford the essentials (food, housing, clothing) that the PPP adjustment indexes off of. (It just couldn't afford any imports.)
Actually I doubt that economists even tried to calculate PPP of China 40 years ago because (even back then) the basket of goods used in the PPP calculation probably included gasoline and cars and such, which only the economic top 1% of China could afford 40 years ago, but if you forced the calculation somehow, you'd probably arrive at a GDPPPP/person not much lower than the current GDPPPP/person (i.e., China has grown spectacularly in GDP/person, but not in GDPPPP/person)
The difference now is that China makes a ton of consumer goods itself, so whereas 40 years ago Chinese PPP would have required forex, now it can be done internally.
That shift opens the possibility of GDPPPP changes in excess (or under) strict GDP per capita growth.
That is because of China and US positions in the global system over this time. The wage/labor/inequality story is broadly true across the global north; China can credit forward thinking central planning, social programs, and industrialization for its economic progress (yet it continues to live under authoritarian rule).
I guess if you have the opportunity to have your stuff made by cheap or free labour whether low paid Chinese or AI robots, societies have a choice how to distribute the benefits which has varied from everything to the rich in the US to fairly even in France say. Such choices will be important with AI.
is a very US thing. In China they've probably 10xd over that time.