Propose-select on Twelve HTTP status codes, by the book

The current HTTP Semantics specification is RFC 9110 (https://www.rfc-editor.org/rfc/rfc9110.html). I found no newer document that replaces it. All twelve codes are defined in its Section 15.

Heuristic cacheability. Section 15.1 names the codes defined as heuristically cacheable: "200, 203, 204, 206, 300, 301, 308, 404, 405, 410, 414, and 501 in this specification". Of your list, that covers 203, 206, 308, 405, 410, 414 and 501. The sections for 303, 307, 413, 421 and 422 make no such statement and none of those codes is on the list, so they are marked false.

Reason phrases. 413 is now "Content Too Large" (it was "Payload Too Large" in RFC 7231). 422 is now "Unprocessable Content" (it was "Unprocessable Entity" in the WebDAV registration).

Sources. Every quote is taken from the code's own section of RFC 9110, and every url is the page I opened.

{"answers":[
{"code":"203","reason":"Non-Authoritative Information","section":"15.3.4","heuristicallyCacheable":true,"quote":"A 203 response is heuristically cacheable; i.e., unless otherwise indicated by the method definition or explicit cache controls (see Section 4.2.2 of [CACHING]).","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"code":"206","reason":"Partial Content","section":"15.3.7","heuristicallyCacheable":true,"quote":"The 206 (Partial Content) status code indicates that the server is successfully fulfilling a range request for the target resource by transferring one or more parts of the selected representation.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"code":"303","reason":"See Other","section":"15.4.4","heuristicallyCacheable":false,"quote":"This status code is applicable to any HTTP method.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"code":"307","reason":"Temporary Redirect","section":"15.4.8","heuristicallyCacheable":false,"quote":"Since the redirection can change over time, the client ought to continue using the original target URI for future requests.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"code":"308","reason":"Permanent Redirect","section":"15.4.9","heuristicallyCacheable":true,"quote":"A 308 response is heuristically cacheable; i.e., unless otherwise indicated by the method definition or explicit cache controls (see Section 4.2.2 of [CACHING]).","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"code":"405","reason":"Method Not Allowed","section":"15.5.6","heuristicallyCacheable":true,"quote":"A 405 response is heuristically cacheable; i.e., unless otherwise indicated by the method definition or explicit cache controls (see Section 4.2.2 of [CACHING]).","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"code":"410","reason":"Gone","section":"15.5.11","heuristicallyCacheable":true,"quote":"A 410 response is heuristically cacheable; i.e., unless otherwise indicated by the method definition or explicit cache controls (see Section 4.2.2 of [CACHING]).","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"code":"413","reason":"Content Too Large","section":"15.5.14","heuristicallyCacheable":false,"quote":"If the condition is temporary, the server SHOULD generate a Retry-After header field to indicate that it is temporary and after what time the client MAY try again.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"code":"414","reason":"URI Too Long","section":"15.5.15","heuristicallyCacheable":true,"quote":"A 414 response is heuristically cacheable; i.e., unless otherwise indicated by the method definition or explicit cache controls (see Section 4.2.2 of [CACHING]).","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"code":"421","reason":"Misdirected Request","section":"15.5.20","heuristicallyCacheable":false,"quote":"A proxy MUST NOT generate a 421 response.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"code":"422","reason":"Unprocessable Content","section":"15.5.21","heuristicallyCacheable":false,"quote":"The 422 (Unprocessable Content) status code indicates that the server understands the content type of the request content (hence a 415 (Unsupported Media Type) status code is inappropriate), and the syntax of the request content is correct, but it was unable to process the contained instructions.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"code":"501","reason":"Not Implemented","section":"15.6.2","heuristicallyCacheable":true,"quote":"A 501 response is heuristically cacheable; i.e., unless otherwise indicated by the method definition or explicit cache controls (see Section 4.2.2 of [CACHING]).","url":"https://www.rfc-editor.org/rfc/rfc9110.html"}
]}