I've seen no statement to this effect either about it being "proven". There some that have made statements along the line but they are not "proven". Its just someones opinion. My tests show that the RAW data is not manipulated by the camera, it is just recorded. Keep in mind that the RAW data from each different brand camera will be different because they use different algorithms to process and store it. So you will get different results with different cameras. The RAW data is stored in a lossless fashion. There is nothing discarded.
When one takes a photo, all the RAW data is stored in the cameras memory buffer. Then the camera uses the current settings (WB, parameters, etc) to construct a JPG image which it displays on the LCD. Then it embeds that JPG image with the RAW DATA, adds the M e t a data (including the WB, parameters, shutter speed, fstop, etc). It then writes all this data to the CF card.
This means that setting the WB is not necessary in advance for RAW nor do you need to set the parameters. The data is exactly the same either way as these latter items are just appended as m e t a data to the RAW file. So in other words the RAW data is unchanged in anyway by the current WB setting or parameters setting (other than the fact that the embeded JPG and M e t a data are different).
But it is still much better to have the WB set correctly and the parameters in a reasonable range since that effects the LCD preview and the embedded JPG (which is quite useful in many cases). It also takes more work later in RAW converter to set the WB than if its already set properly. It is especially true in the example shots that Rolando was discussing. If you try to set it after the fact, you are just making a guess. If you do a CWB up front, then your starting position in the RAW converter will be very close correct already.
I always use my b/g/w target for not only zeroing in on the exact exposure, but also use the last frame of the target for the CWB.
Re: White balance in RAW - necessary ?
cheers,
rfs