I am using GeoServer v2.10.1. I have created a layer for testing using "Geo-tiff" store and later published it that computed "Native and Declared" Coordinate reference systems and computed "Bounding Boxes" automatically from image raster/data.
After creating layer I called WCS GetCapabilities operation and found my layer/coverage in available coverage. Next I have tried calling WCS DescribeCoverage Operation and found that the coordinates under Bounding Box are rotated as shown in figure.
For the confirmation I tried GetCoverage Operation on same coverage and the image downloaded was also rotated.
So is this default WCS behaviour? As I have tried the same layer using WMS (in OpenLayers) and get the correct image.