More generally, I'm not sure we should even say this in the Emacs
manual, as these features belong to the desktop, not to Emacs.
This section of the manual already describes how to start Emacs from systemd,
which isn’t part of Emacs either.
systemd support code is in emacs.c, so that is (borderline) okay.
What you describe is just normal desktop invocation, AFAIU.
+may use the @dfn{Emacs (Client)} menu entry to connect to an Emacs
It is wrong to use @dfn here, since this is not new terminology you
are introducing. Better use @samp.
+server with @command{emacsclient}. If the daemon is not already
+running, it will be started for you.
^^^^^^^^^^^^^^^^^^^^^^^^^^
Please try rephrasing this to avoid passive tense.