By the definition, you are absolutely right in saying that washing machines are not continuous loads. I look at this situation a little differently though. The only time, with rare exceptions, that you would even have two washers to put on the same circuit would be in a commercial laundromat or apartment complex laundry room setting. In these settings, it would be obviously impossible for a washer motor to run for at least three hours straight without interruption, due to the fact that the machines' washing cycles would be shorter then that period of time. What does seem probable, however, is that these machines could be run for eight or ten hours straight with only 3 to 4 min shutdowns for a new load to be thrown in. For my money, that is close enough to a continuous load to warrant 1 extra 20A breaker and homerun. Certainly not code requirement for a dedicated homerun, but certainly good practice IMHO.