RELAX NG Schemas missing some standard steps

[birdya22]

I used the RELAX NG Schemas to validate a XProc pipeline and got the following error:
element "p:message" not allowed here; expected the element end-tag, element "p:add-attribute", "p:add-xml-base", "p:archive", "p:archive-manifest", "p:cast-content-type", "p:choose", "p:compare", "p:compress", "p:count", "p:css-formatter", "p:delete", "p:directory-list", "p:documentation", "p:error", "p:file-copy", "p:file-create-tempfile", "p:file-delete", "p:file-info", "p:file-mkdir", "p:file-move", "p:file-touch", "p:filter", "p:for-each", "p:group", "p:hash", "p:http-request", "p:identity", "p:if", "p:insert", "p:json-join", "p:json-merge", "p:label-elements", "p:load", "p:make-absolute-uris", "p:markdown-to-html", "p:namespace-delete", "p:namespace-rename", "p:os-exec", "p:os-info", "p:pack", "p:pipeinfo", "p:rename", "p:replace", "p:set-attributes", "p:set-properties", "p:sink", "p:sleep", "p:split-sequence", "p:store", "p:string-replace", "p:text-count", "p:text-head", "p:text-join", "p:text-replace", "p:text-sort", "p:text-tail", "p:try", "p:unarchive", "p:uncompress", "p:unwrap", "p:uuid", "p:validate-with-dtd", "p:validate-with-json-schema", "p:validate-with-nvdl", "p:validate-with-relax-ng", "p:validate-with-schematron", "p:validate-with-xml-schema", "p:variable", "p:viewport", "p:wrap", "p:wrap-sequence", "p:www-form-urldecode", "p:www-form-urlencode", "p:xinclude", "p:xquery", "p:xsl-formatter" or "p:xslt" or an element from another namespace

Looking at the xproc31.rnc schema and the list of elements in the error message I can't see the following steps in the StandardStep list:

• p:encode
• p:invisible-xml
• p:message
• p:send-mail