grain['id'] can change without need to reaccept minion public key on master

Description of Issue/Question

according to this page:
https://docs.saltstack.com/en/latest/faq.html#is-targeting-using-grain-data-secure
the grains id can not be changed without re-accepting the minion public key from master
but i can change it on minion with the following command:

salt-call --local grains.setval id NEWID

by refreshing the grains on master:

salt '*' saltutil.refresh_grains

we can see NEWID by:

salt '*' grains.item id

Versions Report

debian /srv/pillar # salt --versions-report
Salt Version:
Salt: 2019.2.0

Dependency Versions:
cffi: 0.8.6
cherrypy: Not Installed
dateutil: 2.2
docker-py: Not Installed
gitdb: 2.0.0
gitpython: 2.1.1
ioflo: Not Installed
Jinja2: 2.9.4
libgit2: Not Installed
libnacl: Not Installed
M2Crypto: 0.24.0
Mako: 1.0.0
msgpack-pure: Not Installed
msgpack-python: 0.4.6
mysql-python: 1.2.3
pycparser: 2.17
pycrypto: 2.6.1
pycryptodome: Not Installed
pygit2: Not Installed
Python: 2.7.9 (default, Sep 25 2018, 20:42:16)
python-gnupg: Not Installed
PyYAML: 3.11
PyZMQ: 14.4.0
RAET: Not Installed
smmap: 2.0.1
timelib: Not Installed
Tornado: 4.2.1
ZMQ: 4.0.5

System Versions:
dist: debian 8.11
locale: UTF-8
machine: x86_64
release: 4.9.0-0.bpo.8-amd64
system: Linux
version: debian 8.11

Start with the FAQ section on secure grain targeting and reproduce the reported sequence using salt-call --local grains.setval id NEWID, salt '*' saltutil.refresh_grains, and salt '*' grains.item id. Compare the observed grain change with the documented public-key requirement and the expected behavior for the reported Salt 2019.2.0 environment.