Styles coming from `__experimentalStyles` are not enqueued in the post editor for themes without `theme.json`

[oandregal]

Raised at #45731

Steps to reproduce:

• Activate the TwentyTwenty theme.
• Load the post editor.
• Add a pullquote block.
• Search for .editor-styles-wrapper .wp-block-pullquote.

The expected behavior is that there should be a style rule containing the font size and line height defined in the __experimentalStyle of the pullquote block embedded into the HTML document. However, that style rule is not present.

[carolinan]

This could be done with a conditional add_action( 'enqueue_block_editor_assets', 'global-styles' ); But it adds all the global styles.
Are we looking for a solution that only adds the styles from block.json __experimentalStyle?

[carolinan]

Should the style not be added to classic.scss? It is loaded with https://developer.wordpress.org/reference/functions/wp_enqueue_classic_theme_styles/
In 6.2 it uses wp_theme_has_theme_json() :

function wp_enqueue_classic_theme_styles() {
	if ( ! wp_theme_has_theme_json() ) {
		$suffix = wp_scripts_get_suffix();
		wp_register_style( 'classic-theme-styles', '/' . WPINC . "/css/classic-themes$suffix.css" );
		wp_enqueue_style( 'classic-theme-styles' );
	}
}