From the “Serverflags” (note the miscapitalisation) Section in man Xorg.conf:
- Option DefaultServerLayout layout-id
- This specifies the default ServerLayout section to use in the absence of the -layout command line option.
From man Xorg: “By default the first Layout section is used.”
The table of Contents lists no “Layout” section, only ServerLayout (and, again, inconsistently titles it “Serverlayout”).
Make of this crap what you will.