Default basic WordPress search doesn’t search Advanced Custom Fields for that article. Is it normal? If there is no solution currently can I request this feature?
The basic WP search only searches in the content of the post, you need to build something or use a plugin if you want to search custom fields. I generally use this one https://wordpress.org/plugins/search-everything/
I have used Facetwp can configure the fields and taxonomies to search on. Facetwp is also designed to work with ACF