I’m not sure exactly what the problem is. update_field() returns the same thing that update_post_meta() returns. Either true the field was updated or false the value was not updated, and ACF does not alter what is returned by update_metadata() so this is working the same way that WordPress core works. If you notice the ticket you linked to is closed and not going to be fixed.
Basically there can’t be an error, either the value was updated or it wasn’t.
I’ve dug through the WP code and the only time anything other than true or false is returned is if a add_post_meta() is called. In this case the meta_id is returned and that is what ACF will return.
I’ll mark this for the developer to look at. Please give more detail on how this is not functioning the same way that WP core functions.
