With the new system preference in 19.05 that works with GDPR, it was brought to our attention that the original system preference GDPR_policy is not in the 18.11 manual. It is in the 19.05 manual.
Right now, we don't have enough resources in the docs team to backport corrections/additions to older manuals. It is unfortunate, but I don't think this will be corrected any time soon. Sorry :(