Description

In a project, while adding the following asset, I noticed it is not registed in Query Monitor:

'header-footer' =>
[
	'types'       => [ 'script', 'style' ],
	'script_args' => [ 'load_method' => 'defer' ],
	'style_args'  => [ 'load_method' => 'async' ],
],

@goodguyry confirmed here the reason.

async style loading is different from async js loading. async doesn’t exist for styles, it’s a hack. it sets the stylesheet as a print stylesheet, which allows it to load but keeps the browser from applying the styles. then once the file is loaded, the print media attribute is replaced, at which point the browser applies the styles.

Use Case

Stylesheet assets added by this plugin appear in Query Monitor, just like assets added by wp_enqueue_style. Even though they have different implementations, they should be visible to a developer.