“That document” is the MCP spec. What is says _is_ MCP, regardless of your understanding of it.
It’s not a “mandate” it’s a specification for how the protocol works. If the connection isn’t stateful, then it isn’t adhering to the specification.
I mean also like… how is it stateless? For both example transports (stdio and SSE) a connection must be maintained.
ANY connection must be initialized via an MCP message and both server and client must negotiate capabilities.
Those capabilities must be honored through the entire lifetime of the connection.
That alone is state.
I suggest you read the spec…