The dial and crystal are only reflecting what there is (to reflect). If there are items/things that cause reflections, block them off. Yeah you can use a black reflector card too, but it might create noise because the dial needs light as well. Plus that kind of cards are difficult to position so that they are not blocking light from the strap/bracelet and creating noise. I don't use any of that stuff.
If the light exposure has been set correctly + you're using a tripod the dial isn't reflecting anything (providing you shoot in a dark room) where only the lightbox is lit.
For pictures like that WM9 Sub above... well there is only the white transparent lightbox roof. i.e no reflections because the "roof" is smooth and blank. I use a transparent plastic flower pot as a lightbox (perfect) and 3-4 lamps. 2 on the both sides, 1 on the back and (sometimes) 1 on the roof (when the dial pattern is special and needs extra attention) like the SMP.
Sub must be the easiest watch in the world to shoot. SMP is tougher as you have to keep the bracelet details visible and capture the "pattern" simultaneuously. You can't do stuff like that with post processing, you have to get the light exposure correct.