As can be seen from the edit history, I am following and update the HowTo whenever needed. Last time I checked occ only changed the config.php, which leads to a new oc_storages entry, but does not remove the old one. While this may work, since it is generally not officially supported, hence not tested, it is advised (by Nextcloud engineers) to not leave the duplicate entry in place, to avoid any possible (now or future) problems.
But even for the config.php entry, I’d keep the sed in place, which replaces really any occurrence of the old path, not just the datadirectory entry. skeletondirectory, templatedirectory, logfile, logfile_audit, apps_paths, tempdirectory. mount_file, etc quite a bunch of settings which can contain the full data directory path as well.