You can’t override the terms shown. ACF does not have a filter for doing this and I don’t think it can be done unless you want to build a custom field type that does this. That’s a lot of work.
My suggestion, and how I would do this would be to use a standard select field. I would dynamically generate the values for the field using your code. https://www.advancedcustomfields.com/resources/dynamically-populate-a-select-fields-choices/. If I wanted the terms assigned to the posts in WP I would create and acf/load_value and acf/update_value filters so that I could get and set the terms. https://www.advancedcustomfields.com/resources/acf-load_value/, https://www.advancedcustomfields.com/resources/acf-update_value/
