Do you think this person had a bad experience and felt the need to "warn" you? It would have been nice had she given a reason.
I have used white, white on white, off-white, cream, linen....
The lighter colors show dirt more, any seams pressed toward the light show more, but that's the only thing I can think of. There is no "ghost of the white fabric" haunting the unsuspecting quilter.
BTW, Peroxide does take blood out of white fabric. I just tested that.