syslinux class uses the following variables, but none of them are coming with any default value - SYSLINUX_CFG - LABELS - INITRD Furthermore most of the used variables are not documented besides in-file comments
As per several other bugs opened of this type, we are not adding default values for the sake of it. I do agree we should document variables where possible.
See: https://bugzilla.yoctoproject.org/show_bug.cgi?id=15759