Also of note, if you have not seen already in the referenced article from above:
"If you use an OSC camera of make ZWO, caution is advised when the 'native' camera driver is used: the ZWO SDK enables the user in the acquisition software to control settings that influence the white balance of a displayed color image. This is achieved by two parameters, WB_R and WB_B, data range 1 to 100, the default values are WB_R = 52 and WB_B = 95. The intensities of the red channel will be multiplied by WB_R/50 and the intensities of the blue channel by WB_B/50. Unfortunately the results of this multiplication are also written to disk in the FITS file. So it is important to set the values of both parameters to 50 and subsequently apply 'Save Config'; only in this way, the real raw intensities will be saved to disk in the FITS files, see . Since the data coming from the camera are saved in FITS files which usually have the number format 'unsigned 16-bit integer', otherwise rounding errors and clipping of high values will arise. Such a complication is generally avoided when the ASCOM camera driver is used instead of the native driver."
This explains the issue. So with FITS files you probably wont be "loosing" any data, just making it harder for some processing applications/workflows to deal with it easily.