Documentation of in-place upgrade is ambiguous about preserving config and credentials

[FireStormOOO]

Documentation describing the SONiC to SONiC in place upgrade process is ambiguous about what happens with existing configuration, and what if anything is copied to the new root.
https://github.com/sonic-net/SONiC/wiki/SONiC-to-SONiC-update
https://github.com/sonic-net/SONiC/blob/master/doc/SONiC-User-Manual.md#323-upgrade-or-downgrade-version

The latter link suggests that config was at one point copied, but this output does not appear in current versions:
Command: cp /etc/sonic/minigraph.xml /host/

The documentation should indicate if the switch configuration will be preserved, as well as the administrator's SSH keys, etc. If the writable portions of the filesystem don't get copied, broader discussion of booting into the updated image with minimal disruption would be beneficial. If the default assumption is that all local state gets blown away on upgrade this should be called out.