One guy has done a nice work decompiling the BIOS and found that skipping over the hidden BIOS pages is hard-coded into the firmware. See this https://forums.lenovo.com/t5/Linux-Discussion/Installing-Ubu...
I'm sure anyone with enough knowledge to decompile a BIOS would have obviously thought of that idea though. I'm guessing the BIOS images are signed or something?
Regardless, this smells evil to me...