I think I see the point about wiring two motors in parallel. Depending upon the motor design you might not want both "up" and "down" feeds paralleled together when only one is connected to the source at a time. You could get some unwanted interaction.
However.....
Looking at the diagram, why are they insisting that the neutral be fed via the control switch? If the neutral was just connected straight through at the box, then you could actually use the second half of the DPDT switch to operate a second motor simultaneously without the paralleling of the "unused" winding becoming an issue.
Re shades bouncing at the end of travel, do the motors/mechanisms have limit switches?
