Materialist dialectics rejects that any definition we come up with to describe something will ever accurately capture it as it exists in the real world, because everything contains internal contradictions and only exists in its interrelations with everything else. In a sense, definitions are all abstractions which only approximate reality, and so we instead define things based on their dominant characteristics. There will never be a society that fits the definition of capitalism or socialism perfectly, so we instead focus on what are the dominant characteristics (principle aspects) of that society.
As Mao explained, whatever is the principle aspect will shape everything else, it will shape all contradictory aspects and those contradictory aspects will take on characteristics of the principle aspect. Take public property for example. Most capitalist states have public property on paper, but does that mean they are socialist? No, because in a state overwhelmingly dominated by private capital, capital owners will control the state, and thus the public sector will ultimately exist at the behest of private interests and will take on a private character.
On the other hand, consider a society that is dominated by public ownership but contains a single private enterprise. That private enterprise will have to acquire its land and all its resources to produce its product from the public sector, and then when it sells its product, it would be selling to workers of the public sector, ultimately selling to public enterprise. So, the public sector would control all of its inputs and outputs, its supply and demand, and thus the private enterprise would effectively be under the control of the public sector and would therefore take on a public character. Hence, such a contradictory aspect within a socialist society would not be sufficient reason to say it is not socialist.
Hence, what makes state capitalism state capitalism is when capital owners nationalize industries but the capitalist class still remains in control of the state, and thus they are operated within the framework of the interests of capital and profits and still retain their capitalistic character.
Liberal society likes to separate things into the "private sector" and "the government/state sector" when in reality private enterprise are forms of local governance that are recognized and defended by the state, and thus are ultimately part of the state and not separate from it. A more coherent analysis would be to separate society into the autocratic and the democratic sector, as this is more close to what is meant when Marxists talk about public vs private property.
To own something means to have a say in its use, and so for a sector to be genuinely public it must be democratic, the working masses have to have input. Nationalization thus does not necessarily mean the transfer from private to public property. The state can still operate property privately. Even if the state nationalizes everything, it is still capitalism if it is still operated at the behest of private interests and not for the masses. When I think state capitalism I think of something like Saudi Arabia where much of the economy is owned by the state but the royal family is recognized as the private owners and they don't even pretend that the working masses have any say. Or I think of modern Russia where on paper they have significant public ownership over the economy but the country is clearly controlled by private oligarchs and so these aren't being put in service of the people; social services are crumbling.
Also, Maoists are pure moralists, don't pay them much attention.