@x23piracy Because there is a difference.
Typically for bios (legacy) mode the exit mode is SANBOOT (that is the way iPXE attempts to location the hard drive). For uefi system the best exit mode is rEFInd, which is an external program that is used to find the boot drives. You may be able to tweak the refind.conf file to look for legacy stuff but I haven’t tried it.
There is something I just discovered the other day while I was hacking FOG’s boot menus. That is the platform variable. ref: http://ipxe.org/cfg/platform you can use that in your boot local section to test to see if the platform is efi or pc-bios and then select the best exit mode there.
such as in: (warning I just glued this code together there is no testing done)
:bootlocal
iseq ${platform} efi && goto boot-efi || goto boot-bios
goto MENU
:boot-efi
<don't know the syntax for refind> || goto MENU
:boot-bios
sanboot --no-describe --drive 0x80 || goto MENU