Almost certainly not noticeable in WHAM KABLAM BANG metal, but it's easy enough to do, so might as well I say! (especially since there's a dither thing built into the almighty Voxengo Elephant)
Exactly, how this step is achieved?
dithering vs truncating
your basically cutting away some of the room information, if you truncate from lets say 32 to 16 bits. the first 16 bits will then get "cut".
remember, the lower bits represent your room / ambience.
with dithering, you basicalley preserve depth in your mix.
as its not hard to do, you should always dither after you've done all fades.
the last thing you would do in a mastering chain is:
dither to 16 bit