Yep, feet can get smaller (and often do) once you start hormones. Mine shrunk two EU sizes and I was a bit confused at first, but then other people on hormones told me that the exact same thing happened to them once they started.
At first I was all confused as to how it can be, but then it was explained that it's just a reduction in cartilage and changes in connective tissue. There's a whole heap of surprising things that happen on hormones and that aren't discussed as widely.