Using your logic, which isn't based on a shred of actual evidence, feet would also shrink on lasix, hydrochlorothiazide, bumetonide, etc. They don't, unless there was edema prior to prescription. Edema sufficient to raise a foot size in the typical young, otherwise healthy trans female is quite unlikely.
In general, MTF's do not experience reduction in foot size. Exceptions to this rule generally occur in those cases where there is significant weight loss. The underlying skeleton is unaffected, and most of the muscle which moves the foot actually resides in the lower leg.