I'd assume that with the way new machines are, if you added water with the "sink" before the wash, it would just drain it automatically when it senses more than a few drops in the sump. And I'm sure the little water spicket is locked out once a cycle begins.
It could be useful for small items but with our lazy society I'm sure it'll just sit in a closet or be stuffed behind the machine to collect dryer lint.
The LG pedestal washer, however, I could see using that. There are three white button ups with colored stripes on them in this entire house, but they're never dirty at the same time, and I don't really feel washing one shirt in the giant washer is necessary, but I also don't want to wash it with the normal whites with bleach, so that mini washer could prove useful in that situation.