This is an old one and you should probably submit it to the developer here https://support.advancedcustomfields.com/new-ticket/, I reported it to him when a year ago, but he does get busy with other things that need to be done.
@andrija findings are correct. For specific field types it works correctly. When applying it to every field with the generic hook content only gets added before. From what I remember, this has something to do with the JavaScript rendering of the field.
