There are fewer flights/itineraries.
Chinese authorities have imposed a strict policy regarding international flights with quotas and circuit-breakers ("Five Ones Policy", article on this from Chinese Wikipedia). The number of seats is also limited to 75% of ordinary capacity.
Under "Five Ones Policy", for most international routes, one ...
Not really, probably because almost all China Railway trains require a reservation under your real name and a pass really doesn't make anything more convenient. Some suburban lines used mainly for commuting now allow riding without a reservation, but the vast majority of trains require reservations.
So a pass wouldn't really help out in this case, because it ...
I mean, yes, the sources you cited are generally right. I'm speaking from experience here, so I don't have data, but I believe my experience to be generally reliable. For long distances, there are a lot (I mean a LOT) of discounts on flights, but hardly any for the railways.
I picked a random date and a random pair of large cities that are quite far away ...
Look it up on https://covid19.trackvaccines.org/vaccines/.
E.g., currently, for Sinovac: CoronaVac
, it is approved in 25 countries:
Lao People's Democratic Republic