On Windows, Qualcomm uses the SCM driver to hook the Get/SetVariable implementation and replace it with their own. The UEFI standard SetVariable implementation

On Windows, Qualcomm uses the SCM driver to hook the Get/SetVariable implementation and replace it with their own. The UEFI standard SetVariable implementation is nonfunctional and the GetVariable one is at the same state since ExitBootServices. This is due to the fact that the firmware and the OS cannot control the storage device at the same time. The issue isn't seen on most x86 PCs since those use a separate SPI flash chip for the UEFI.