wouldn't the refrigerator have to work a lot harder in that case to remove the extra heat? doesn't seem beneficial from an energy use perspective, considering you have to pay to heat the water, then cool it again.
That was my initial reaction too, but upon consideration, how long does it take for hot water to get down the line? Typically, both the hot and cold water lines are full of room-temperature water until you run them long enough to heat up all of the piping between source and sink. I'm having trouble picturing an in-home ice maker having enough throughput for it to actually matter.
This is the reality of the matter, though there may be some minor benefit to "using up" hot water a bit more. Practically it's unlikely to matter either way.
