Multipass compositing problem


Hello, I´m try to learn mulitpass compositing postproduction in photoshop. I use vray 3dsMax, I export passes to one exr, open in photoshop as 32bit format. Then I change to mode of layer to linear dodge (add) and it give me same result as rgb original image. Problem starts when I change image format from 32 to 16bit. Then passes stop giving the same result as rgb image. Do I something wrong? or is it normal.
in this video not hapens after conversion to 16bit
thank you