An athlete squatting big weights should have incredible core strength, at least in theory.
Perhaps it also depends on the built of an athlete. Picking between a tall 192-195cm athlete with long legs (hip height 118-121cm) and strong core area (no. of weekly sit ups - 2000) and a shorter 175-180cm athlete of medium built and relatively conditioned core area (who does only up to 150 sit ups a week), IMO squats should suit more the shorter athlete i.e. the shorter athlete would be able to squat more, in this instance even though his core may be slightly less strong. Then you take Timmermann or Günter Werner for example …and they blow this theory out of water.