You can simoply export the S2 product to NetCDF or Envi format and you will get.
If you export to GeoTiff you get the DN values.
In order to prepare the product for the GeoTiff export you can create new bands by Band Maths.
Simply use the band name as expression, set a new name and preserve the wavelength, also disable the virtual option. Afterwards you can delete the original band.
If you want to do it on a stack of products you can do it with a graph file on the command line.
