A bit of both. My computer does not have the "service" command at all. While it's true that many systems still do, it's typically there as a legacy compatibilit

A bit of both. My computer does not have the "service" command at all. While it's true that many systems still do, it's typically there as a legacy compatibility layer, to translate SysV style commands to systemd. So while the command might work for many readers, I don't think it's a good idea to send beginners that way, and its inclusion (without any footnotes or other qualifications) suggests that the author's knowledge is out of date.