These values are used in the built in functions get_metadata() https://codex.wordpress.org/Function_Reference/get_metadata and update_metadata(). The values in the code you referenced are the only ones this function allows. ACf does not do the queries directly and depends on WP do to the work.
You may find some inspiration here on how this might be possible https://awesomeacf.com/storing-acf-data-custom-database-tables/
