Only file CSS assets with preprocessing enabled can be optimized

Problem/Motivation

CssOptimizer Exeption: Only file CSS assets with preprocessing enabled can be optimized
https://git.drupalcode.org/project/drupal/-/blob/11.x/core/lib/Drupal/Co...

Array ( 
  [weight] => -9.9998333333333 
  [group] => 0 
  [type] => file 
  [data] => themes/contrib/stable/css/system/components/align.module.css 
  [version] => 10.2.2 
  [media] => all 
  [preprocess] => 
  [license] => 
    Array (
	[name] => GNU-GPL-2.0-or-later 
	[url] => https://www.drupal.org/licensing/faq [gpl-compatible] => 1 
  ) 
)

Steps to reproduce

$config["system.performance"]["css"]["preprocess"] = TRUE;