ACF uses the built in WP search for getting the results of these fields. This search looks for your entered text anywhere in the title and content of the post. To do what you want you’d need to alter the way WP does searches.
See this topic https://support.advancedcustomfields.com/forums/topic/acf-page-link-search-by-title-only/. In your case you’d want to query to have % only at the end of the search terms.
