When you say “ACF Starter Kit”, if you are talking about the ACF Field Type Template then some explanation.
There is not need to actually create filters for the methods that are included in your new field type. These filters and actions will be automatically called by ACF because all of these actions are added by ACF for every field type.
ACF also uses the same filters that are supplied for use to use to do what it does.
For example, the acf/update_field hook not only calls custom filters added by others in themes but also runs these filters associated with each field type.
I’m not exactly sure what your looking for, but there is not need for you to actually update the post meta with a value in your field. ACF will do this automatically.
$original_value will not contain the old value from the DB, this will contain the value that was originally submitted while $value will contain the results of any other acf/update_value filters that have acted on the submitted value.
