Internal Page Cache not used

On a Drupal 9.5.1 website where both Internal Page cache and Dynamic Page cache modules are enabled, I don't see any header regarding Internal Page Cache as soon as this module is enabled.

Is it expected behavior ?

Cache-Control: must-revalidate, no-cache, private
Content-Encoding: br
Content-Language: en
Content-Security-Policy: frame-ancestors 'self'
Content-Type: text/html; charset=UTF-8
Date: Mon, 16 Jan 2023 11:59:26 GMT
Expires: Sun, 19 Nov 1978 05:00:00 GMT
Server: nginx
Transfer-Encoding: chunked
Vary: Accept-Encoding
X-Content-Type-Options: nosniff
X-Content-Type-Options: nosniff
X-Drupal-Dynamic-Cache: HIT
X-Frame-Options: SAMEORIGIN
X-Frame-Options: SAMEORIGIN
X-Generator: Drupal 9 (https://www.drupal.org)

When uninstalled:

Cache-Control: max-age=900, public
Content-Encoding: br
Content-Language: en
Content-Security-Policy: frame-ancestors 'self'
Content-Type: text/html; charset=UTF-8
Date: Mon, 16 Jan 2023 12:04:33 GMT
Etag: W/"1673870672"
Expires: Sun, 19 Nov 1978 05:00:00 GMT
Last-Modified: Mon, 16 Jan 2023 12:04:32 GMT
Server: nginx
Transfer-Encoding: chunked
Vary: Accept-Encoding
Vary: Cookie
X-Content-Type-Options: nosniff
X-Content-Type-Options: nosniff
X-Drupal-Cache: HIT
X-Drupal-Dynamic-Cache: MISS