Peter, they do have a prewash.
But it's not automatic, to avoid those hosekeepers that always run the prewash for everything, even when it's not necessary (and consequently save millions of gallons of water around the world)
how to manually prewash at affinity (old version, the same as I have):
Choose spin only, extra rinse, no spin (or low speed spin if you prefer), add detergend in the drum, close, press start imediatelly.
If you choose no spin it will take 8 minutes prewashing and 2 minutes draining.
If you choose any other spin speed, the cycle takes 18 minutes.