\Perhaps it is just the symbol that mislead me. It looks like the contacts of that first relay only have power when the pushbutton is pressed.Look at the relay diagram again. In the rest state (SW1 open), both sides of the motor are grounded. Note that K1 is an impulse relay, and there is no standard schematic symbol for this critter. Each time it is actuated, it changes state and latches there even when power is removed. When the button is pressed again, K1 changes to the other state and latches there. Each time SW1 is pressed, K1 changes state and energizes one of the two motor relays, whichever one was not energized on the previous button press.
As noted, K1 acts as a toggle flipfllop. with the added feature that it does not require any power to retain its last state. Alternately, each motor relay is activated as long as SW1 is pressed, then returns its side of the motor to GND when SW1 is released.