[9.6-6] MUST NOT: A server that receives a "close" connection option MUST NOT initiate closure of the connection (see ...

[saviorand]

RFC 9112 Requirement

Section: 9.6-6
Keyword: MUST NOT

A server that receives a "close" connection option MUST NOT initiate closure of the connection (see below) after it sends the final response to the request that contained the "close" connection option. The server SHOULD send a "close" connection option in its final response on that connection. The server MUST NOT process any further requests received on that connection.¶

Reference: https://www.rfc-editor.org/rfc/rfc9112.html#section-9.6-6