If you want to use detector rails to activate an attached single or string of powered rails that are going 'up hill' on a series of stair step blocks, when your mine cart passes over the detector rail, it does NOT active the powered rails attached above it on the hill. If you do the same action, only on a flat surface, it works perfectly, as described by your documentation. A temp workaround I have found is to put a redstone torch on a block next to one of the powered rails, and then they are all activated, but will never deactivate as long as the torch is present. However, they shouldn't need to be active all the time, which is what the detector is for. I have attached an image shows the setup.