My own shrinkage is not that dramatic. I went from a fairly-tight U.S. 10 to a very comfortable 9.5 and sometimes 9. Although what causes the foot to shrink is debatable, that it does in many transwomen is hard to dispute, unless we are under some collective cinderella step-sister fantasy. I have also lost an inch+ in height (as have many of my other sisters). What I find more peculiar is this. My left foot has always been slightly larger than my right. I always used it as the guide for buying shoes. But recently, my feet have evened out, and the right may actually be slightly larger than the left.
I love you all, regard of foot size.