geoffc: Yup, good question, the same one I asked in this post last month. To quote:

Apparently in upgrading its Shenzhou manned spacecraft China has made it 0.3 meters longer and about four tons heavier. In fact, this manned ferry for getting to and from its space station is as heavy as a standard module used on both Mir and ISS. I could be wrong, but if this is the case they will require the Long March 5 or 5B for every manned flight. Since this rocket is large and expensive, it will be difficult to use it for maintaining a frequent launch pace, thus limiting the number of manned missions.

As I said, I could be wrong. Up until now I had assumed that a variant of the Long March 5 would be used to launch the station modules, and the smaller Long March 2F rocket used to ferry astronauts to it (as was done on all previous Chinese manned missions). This could still be the case.

If not, however, China’s space engineers have either put a limit on what they can achieve by overbuilding that manned capsule, or their government has made a major commitment to put a lot of tonnage into orbit. If the latter China’s space program is going to be quite competitive indeed.