Pixels outside of image area are not image area (in most cases).
Unlike Adobe tools (e.g. DNG Converter), LibRaw tries to save as much image area as possible, without any space for demosaic to run. So, you need to crop slightly more to get demosaic some space.
There is small exclusion from 'as much as possible rule': border size is usually even, to keep bayer patern the same from both edges (uncropped and 'active area' cropped). This is not general rule, but I hold on to it when image format do not dictates other borders (such as DNG ActiveArea or so)
Pixels outside of image area are not image area (in most cases).
Unlike Adobe tools (e.g. DNG Converter), LibRaw tries to save as much image area as possible, without any space for demosaic to run. So, you need to crop slightly more to get demosaic some space.
There is small exclusion from 'as much as possible rule': border size is usually even, to keep bayer patern the same from both edges (uncropped and 'active area' cropped). This is not general rule, but I hold on to it when image format do not dictates other borders (such as DNG ActiveArea or so)