i run wordpress blog on windows apache server....

i want to set X-Robots-Tag "noindex" on every rss+xml content

i tried to use this rule

<FilesMatch "\.(rss|xml)$">
Header set X-Robots-Tag "noindex"
</Files>

i still cant find X-Robots-Tag "noindex" on http header response

Final response 
< HTTP/1.1 200 OK
< Date: Sun, 25 Jul 2021 10:27:42 GMT
< Content-Type: application/rss+xml; charset=UTF-8
< Transfer-Encoding: chunked
< Connection: keep-alive
< X-Powered-By: PHP/7.3.10
< Last-Modified: Sun, 25 Jul 2021 10:28:01 GMT
< Set-Cookie: pvc_visits[0]=1627295281b60; expires=Mon, 26-Jul-2021 10:28:01 GMT; Max-Age=86400; path=/; secure; HttpOnly
< Link: ; rel="https://api.w.org/", ; rel="alternate"; type="application/json", ; rel=shortlink
< Cache-Control: max-age=3600
< Expires: Sun, 25 Jul 2021 11:28:00 GMT
< Vary: Accept-Encoding,User-Agent
< CF-Cache-Status: DYNAMIC
< Expect-CT: max-age=604800, report-uri="https://report-uri.cloudflare.com/cdn-cgi/beacon/expect-ct"
< NEL: {"report_to":"cf-nel","max_age":604800}
< X-Content-Type-Options: nosniff
< Server: cloudflare
< CF-RAY: 6744b
< alt-svc: h3-27=":443"; ma=86400, h3-28=":443"; ma=86400, h3-29=":443"; ma=86400, h3=":443"; ma=86400

could it be due to pretty link alias? since the url end up with "feed" character not rss or xml like this

htttps://www.domaincom/feed

https://www.domaincom/post.html/feed