They said they are even designing a larger rocket with 10m diameter, which is more than Starship (9m). My question is though where they are planning to get the required money from. Unlike the organization behind the Changzheng ("long march") rockets, which is already developing a 10m rocket as well, LandSpace is not state funded. And they don't have a billionaire at the top like Blue Origin and SpaceX.
On the other hand, they were only founded in 2015, and it's impressive what they have achieved since then, no doubt with quite limited funds. They also have some experience with designing methane engines.