.....I'm not sure if it's the pedals or the fact that the pedals have more float and let me......
Never had problems with foot alignment when using clips and straps.....then moved onto first generation of clipless - no float....was decent given the level of shoes at that time. Then after a few years of trying clipless with float I noticed that my left heel wanted to flair outwards.....like the OP. As the years went on it got progressively worse. I also noticed more and more that I was sitting more-so on the right bony protursion of my pelvis (causing saddle sores 90% of the time on the right)....I had a therapist with cycling background check me out once and his determination was that my left leg was very nearly the same length as my right - that my issue must only be just a flexibility/strength imbalance....which I don't think I have to any significant degree. So I tried adjusting the left float cleat to minimize that heel movement and also worked hard to mentally keep things in alignment....finally I went back to fixed cleats - OMG - what a huge improvement
- not only with the left foot but also a better "connected" feeling overall with the bike and a perception of putting more power to the pavement. I don't have before and after power meter numbers to quantify the change but the perceived/actual improvement is real for me.