Windows RT(for ARM) requires the bootloader to be locked like the iPad's is.
Windows 8 on x86 requires the UEFI on PC to provide an option to disable secure boot and allow a physically present user to add any signing keys of their choice. Windows 8 will happily boot on any hardware that does not support UEFI secure boot(most current PCs) and will also boot without any complaints if Secure Boot is disabled by the user.
Note: The above requirement is only to get the hardware Windows 8 certified. Microsoft is legally prohibited from requiring anything from the PC OEMs.
Why is there SO much confusion around this in these parts? I see these exact type of back and forth arguments and utter confusion in almost every discussion related to UEFI or secure boot .
You misspelled ARM.