Some interpolation methods are based on proper lightness calculation. For these methods, demosaic w/o prior white balance will provide wrong (and visually very bad) results.
Also, data scaling in desirable to lower rounding errors.
Anyway, you may create your own dcraw_process() call without steps that are unnecessary to you. In LibRaw's dcraw_process() there is no way to skip pre-interpolations steps (scale_colors, pre_interpolate) /and after-interpolation convert_to_rgb() is also always executed).
Alternatively, you may fix all processing params via user_* variables.
Some interpolation methods are based on proper lightness calculation. For these methods, demosaic w/o prior white balance will provide wrong (and visually very bad) results.
Also, data scaling in desirable to lower rounding errors.
Anyway, you may create your own dcraw_process() call without steps that are unnecessary to you. In LibRaw's dcraw_process() there is no way to skip pre-interpolations steps (scale_colors, pre_interpolate) /and after-interpolation convert_to_rgb() is also always executed).
Alternatively, you may fix all processing params via user_* variables.