Currently when you Lock Orientation this will keep the app ui in Orientation of either Landscape or Portrait.
But say you have set the Orientation to Portrait and turned the Lock Orientation Off, your apps UI will be shown in Portrait at full scale, and at a scaled down version in Landscape mode.
But when your device is upside down, which happens a lot ,especially if you place your phone in a stand, the UI will be shown Upside down, it will not rotate. The UI should rotate to accomodate the device's orientation, Landscape, Portrait both Up and Upside down positions of the device.
I have to place my phone upside down in my stand when charging, there is no room to insert the power cord otherwise. I have to keep testing even if the UI is upside down.