Generally I dont understand how board can turn when planning in footstraps .It dont have rudder


We learned in school that are two ways for steering board:
A) moving sail fore and aft,shifting coe in relation to clr,when non plannning,that is clear.
B)carve board on rails when board is planning,example in jibe when you step on leeward rail,that is also clear.
So I dont understand how can I carve/tilt slalom board when I am planning with both feet in footstraps?
When I look at videos and others slalom sailors,when they bear away sail stay in same position all the time,so they must do somthing with they feet to turn bord downwind..
Look at this video, at 1:15 he bear away,I dont see that he move sail forward,sail stay in same position,but he obviously do something with his feet.Can someone explain what he doing at 1:15 to turn board downwind?