Canting is most effective in a straight line (knee/foot pointed down the ski), so when different planes are working (knee/foot plane off the ski plane), canting becomes a nightmare. Because now, you are not simply bringing the knee back over the center of the ski, but drastically changing the angle from the lower leg to femur and causing it to kink.
Concerning footbeds, a footbed brings the knee back over the second toe (super generally speaking) and if you abduct the foot, this opens your hips in a funny way. Try it out just standing in your shoes. If you abduct your foot, then bring your knee over your second toe, see what it does/feels to your hips, especially with both feet at the same time.