It is a feature, not a bug. That blows. I borked my 2014 Mac mini when I upgraded to High Sierra. I was able to recover, but only with a bootable USB. Again, one trillion dollars! They could assign one guy to every computer they have released in the last ten years doing nothing but installing and configuring it in every way possible and then updating to the next OS to see what happens. The cost would be like a box of tissues to them. We are not talking about Windows where the hardware is of unknown configuration and manufacture. They literally make the operating system AND the hardware! WTF