No backhanded jab intended. I personally don't believe that "bottom surgery" changes sex or gender. I know that many others in the trans community (including those that believe in "brain sex") also share this view, so it seems like a more informed way to refer to this category of procedures, particularly within the context of this thread in which the OP was curious about the "reversibility" of gender reassignment. The way I view it, it is not like some big mystical thing happens. I know that others may not share this view and I respect that, but to attempt to reconcile the divergent views just becomes a "my personal belief system is better than yours" kind of argument that is, in the end, not productive for anyone.